Power line communications system and method of operating the same

ABSTRACT

The present invention provides a system and method for operating a power line communications system for communicating via an underground residential distribution power system. One embodiment of the present invention includes an aggregation point, which may be co-located with a point of presence, communicatively coupled to one or distribution points. The distribution points are communicatively coupled to one or more medium voltage interface devices. The medium voltage interface devices are communicatively coupled to one or more power line bridges via URD medium voltage power lines. The power line bridges may be co-located with a URD distribution transformer and provide communications to the user devices communicatively coupled to the LV power lines of the distribution transformer.

FIELD OF THE INVENTION

The present invention generally relates to data communications over apower distribution system and more particularly, to a power linecommunication system and method of using the same.

BACKGROUND OF THE INVENTION

Well-established power distribution systems exist throughout most of theUnited States, and other countries, which provide power to customers viapower lines. With some modification, the infrastructure of the existingpower distribution systems can be used to provide data communication inaddition to power delivery, thereby forming a power line communicationsystem (PLCS). In other words, existing power lines, that already havebeen run to many homes and offices, can be used to carry data signals toand from the homes and offices. These data signals are communicated onand off the power lines at various points in the power linecommunication system, such as, for example, near homes, offices,Internet service providers, and the like.

While the concept may sound simple, there are many challenges toovercome in order to use power lines for data communication. Power linesare not designed to provide high speed data communications, aresusceptible to interference, and are very lossy at the frequencies usedfor data communications. Additionally, federal regulations limit theamount of radiated energy of a power line communication system, whichtherefore limits the power of the data signal that can be injected ontopower lines.

Power distribution systems include numerous sections, which transmitpower at different voltages. The transition from one section to anothertypically is accomplished with a transformer. The sections of the powerdistribution system that are connected to the customers premisestypically are low voltage (LV) sections having a voltage between 100volts (Vrms, 60 Hz, or “V”). and 240V, depending on the system. In theUnited States, the LV section typically is about 120V. The sections ofthe power distribution system that provide the power to the LV sectionsare referred to as the medium voltage (MV) sections. The voltage of theMV section is in the range of 1,000V to 100,000V. The transition fromthe MV section to the LV section of the power distribution systemtypically is accomplished with a distribution transformer, whichconverts the higher voltage of the MV section to the lower voltage ofthe LV section.

Power system transformers are one obstacle to using power distributionlines for data communication. Transformers act as a low-pass filter,passing the low frequency signals (e.g., the 50 or 60 Hz) power signalsand impeding the high frequency signals (e.g., frequencies typicallyused for data communication). As such, power line communication systemsface the challenge of communicating the data signals around, or through,the distribution transformers.

Furthermore, up to ten (and sometimes more) customer premises willtypically receive power from one distribution transformer via theirrespective LV power lines. However, all of the customer premises LVpower lines typically are electrically connected at the transformer.Consequently, a power line communications system must be able totolerate the interference produced by many customers. In addition, thepower line communication system should provide bus arbitration androuter functions for numerous customers who share a LV subnet (i.e., thecustomer premises LV power lines that are all electrically connected tothe LV power line extending from the LV side of the transformer) and aMV power line.

In addition, components of the power line communication system, such asthe distribution transformer bypass device (PLB), must electricallyisolate the MV power signal from the LV power lines and the customerpremises. Furthermore, a communication device of the system should bedesigned to facilitate bi-directional communication and to be installedwithout disrupting power to customers. These and other advantages areprovided by various embodiments of the present invention.

SUMMARY OF THE INVENTION

The present invention provides a system and method for operating a powerline communications system for communicating via an undergroundresidential distribution power system. One embodiment of the presentinvention includes an aggregation point, which may be co-located with apoint of presence, communicatively coupled to one or more distributionpoints. The distribution points are communicatively coupled to one ormore medium voltage interface devices. The medium voltage interfacedevices are communicatively coupled to one or more power line bridgesvia URD medium voltage power lines. The power line bridges may beco-located with a URD distribution transformer and providecommunications to the user devices communicatively coupled to the LVpower lines of the distribution transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described in the detailed description thatfollows, by reference to the noted drawings by way of non-limitingillustrative embodiments of the invention, in which like referencenumerals represent similar parts throughout the drawings. As should beunderstood, however, the invention is not limited to the precisearrangements and instrumentalities shown. In the drawings:

FIG. 1 is a diagram of an exemplary power distribution system with whichthe present invention may be employed;

FIG. 2 is a diagram of the exemplary power distribution system of FIG. 1modified to operate as a power line communication system, in accordancewith an embodiment of the present invention;

FIG. 3 is a schematic of a power line communication system in accordancewith an embodiment of the present invention;

FIG. 4 is a block diagram of an example PLCS, in accordance with anembodiment of the present invention;

FIG. 5 is a block diagram of a portion of an example PLCS, in accordancewith an embodiment of the present invention;

FIG. 6 is a block diagram of a portion of an example PLCS, in accordancewith an embodiment of the present invention;

FIG. 7 is a block diagram of another example PLCS, in accordance with anembodiment of the present invention;

FIG. 8 is a block diagram of still another example PLCS, in accordancewith an embodiment of the present invention;

FIG. 9 is a block diagram of a portion of an example PLCS, in accordancewith an embodiment of the present invention;

FIG. 10 is a block diagram of an example optical termination point, inaccordance with an embodiment of the present invention;

FIG. 11 is a block diagram of another example optical termination point,in accordance with an embodiment of the present invention;

FIG. 12 is a block diagram of a portion of an example PLB, in accordancewith an embodiment of the present invention;

FIG. 13 is a block diagram of a portion of an example PLB, in accordancewith an embodiment of the present invention; and

FIGS. 14 a-c are functional block diagrams of a portion of a PLB, inaccordance with various embodiments of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as particular networks,communication systems, computers, terminals, devices, components,techniques, data and network protocols, software products and systems,operating systems, development interfaces, hardware, etc. in order toprovide a thorough understanding of the present invention.

However, it will be apparent to one skilled in the art that the presentinvention may be practiced in other embodiments that depart from thesespecific details. Detailed descriptions of well-known networks,communication systems, computers, terminals, devices, components,techniques, data and network protocols, software products and systems,operating systems, development interfaces, and hardware are omitted soas not to obscure the description of the present invention.

System Architecture and General Design Concepts

Power distribution systems typically include components for powergeneration, power transmission, and power delivery. A transmissionsubstation typically is used to increase the voltage from the powergeneration source to high voltage (HV) levels for long distancetransmission on HV transmission lines to a substation. Typical voltagesfound on HV transmission lines range from 69 kilovolts (kV) to in excessof 800 kV.

As shown in FIG. 1, in addition to HV transmission lines, powerdistribution systems include MV power lines and LV power lines. Asdiscussed, MV typically ranges from about 1000 V to about 100 kV and LVtypically ranges from about 100 V to about 600 V. Transformers are usedto convert between the respective voltage portions, e.g., between the HVsection and the MV section and between the MV section and the LVsection. Transformers have a primary side for connection to a firstvoltage (e.g., the MV section) and a secondary side for outputtinganother (usually lower) voltage (e.g., the LV section). Suchtransformers are often referred to as distribution transformers or astep down transformers, because they “step down” the voltage to somelower voltage. Transformers, therefore, provide voltage conversion forthe power distribution system. Thus, power is carried from substationtransformer to a distribution transformer over one or more MV powerlines. Power is carried from the distribution transformer to thecustomer premises via one or more LV power lines.

In addition, a distribution transformer (DT) may function to distributeone, two, three, or more phase voltages to the customer premises,depending upon the demands of the user. In the United States, forexample, these local distribution transformers typically feed anywherefrom one to ten homes, depending upon the concentration of the customerpremises in a particular area. Distribution transformers may be pole-toptransformers located on a utility pole, pad-mounted transformers locatedon the ground, or transformers located under ground level.

FIG. 1 discloses a representative underground residential distribution(URD) system comprising a high voltage (HV) power line that is connectedto a plurality of high voltage transformers (HVT) that steps down thehigh voltage to medium voltage.

The HVT steps down the high voltage to medium voltage for distributionon the medium voltage (MV) power lines which are connected to one ormore distribution transformers (DTs). Each DT further steps down themedium voltage to low voltage (LV) and typically is connected to one ormore LV power lines, each of which may extend to a separate customerpremises (not shown in FIG. 1).

The URD network of FIG. 1 includes two types of topographies. The firsttype is commonly referred to as a ring or “U” topology as represented bynetworks 1 and 2. The ring network may be U shaped with each leg of theU being connected to a HVT. In addition, the ring network may include aswitch SW that connects both sides of the ring together (as in network1). Consequently, should either HVT fail (or a break in the MV powerline occur) the switch may be closed so that the entire MV networkreceives power. Other such networks may not include a switch (as innetwork 2).

Another type of topology is referred to as a radial or star network asshown in network 3 in which one or more MV power lines extend away froma single HVT. While the illustrations of these networks depict a singleMV power line, a radial or ring network configuration may includemultiple MV power lines extending from each HVT (e.g., one or more setsof three cables with each cable of each set carrying one phase of thethree phases in a three phase system).

As is known to those skilled in the art, each DT in the URD network maybe electrically connected to the adjacent DTs via a length of URD cable.The URD cables typically may be terminated (e.g., on each end) via anelbow that plugs into a bushing on the DT. The two cables typically areelectrically connected to each other inside the transformer enclosureand are also connected to the primary of the distribution transformeritself. As discussed, the secondary of the DT is connected to the LVpower lines supplying power to the customer premises. Thus, the seriesof URD cables, and transformers connecting them, form a first (MV)segment of the URD power distribution network and the LV power linesconnected to the DTs form a plurality of low voltage segments.

The URD network may be connected to, and receive power from, an overheadMV power line. Referring to FIG. 2, a URD cable may extend up a utilitypole and terminate with a pothead connector (not shown) for connectionto an overhead MV power line (known as a Riser-Pole). At the other end,the URD cable may terminate with an elbow to be plugged into a bushingat a transformer. As discussed, the URD cables extending between URDtransformers typically will terminate with an elbow to be plugged in thetransformer on both ends. Typically, the URD cable will include a centerconductor, an insulator surrounding the center conductor, a concentricneutral conductor surrounding the insulator, and an external insulatorsurrounding the concentric neutral conductor. In addition, the cable mayinclude one or more sheaths such as a semi-conductive sheath around theinsulator.

Power Line Communication System

FIG. 3 provides a schematic of one embodiment of the present invention,which includes an aggregation point (AP) that may be co-located with apoint of presence (POP) for connection to the Internet and/or othernetwork. The AP 100 may include a conventional Internet Protocol (IP)data packet router and may be directly connected to an Internet backbonethereby providing access to the Internet. Alternatively, the AP 100 maybe connected to a core router (not shown), which provides access to theInternet, or other communication network.

The AP 100 may route voice traffic to and from a voice service providerand route Internet traffic to and from an Internet service provider. Therouting of packets to the appropriate provider may be determined by anysuitable means such as by including information in the data packets todetermine whether a packet is voice. If the packet is voice, the packetmay be routed to the voice service provider and, if not, the packet maybe routed to the Internet service provider. Similarly, the packet mayinclude information (which may be a portion of the address) to determinewhether a packet is Internet data. If the packet is Internet data, thepacket may be routed to the Internet service provider and, if not, thepacket may be routed to the voice service provider.

The AP 100 may be communicatively coupled to one or more distributionpoints (DPs) 200. Each DP 200 may be communicatively coupled to one ormore MV interface devices (MVID) 300. Each MVID 300 may be incommunication with one or more power line bridges (PLBs) 400, via theURD medium voltage power line(s). The PLBs 400 may be in communicationwith one or more user devices that reside in one or more customerpremises CP via the low voltage power lines or via a wireless link. Aswill be evident from the discussion below, communications over the powerdistribution network occur between the MVID 300 and the customerpremises user devices (e.g., via the PLBs). Communications upstream fromthe MVID 300—such as between the MVIDs 300 and their DPs 200 or betweenthe DPs 200 and the AP 100—may be fiber optic, wireless, coaxial cable,T-carrier, Synchronous Optical Network (SONET), any other suitablemedium, or any combination thereof. As will be evident to one skilled inthe art, each network element (e.g., MVID 300, DP 200, or AP 100), wouldinclude a transceiver appropriate for communicating over the selectedmedium (e.g., a wireless transceiver for a wireless link).

The PLCS also may include a power line server (PLS) (not shown) that isa computer system with memory for storing a database of informationabout the PLCS and includes a network element manager (NEM) thatmonitors and controls the PLCS. The PLS allows network operationspersonnel to provision users and network equipment, manage customerdata, and monitor system status, performance and usage. The PLS mayreside at a remote operations center to oversee a group of communicationdevices via the Internet. The PLS may provide an Internet identity tothe network devices by assigning the devices (e.g., user devices, PLBs400, (e.g., the LV modems and MV modems of PLBs), repeaters, MVIDs 300,DPs 200, and AP 100 if necessary) an IP address and storing the IPaddress and other device identifying information (e.g., the device'slocation, address, serial number, etc.) in its memory. In addition, thePLS may approve or deny user device authorization requests, commandstatus reports and measurements from the PLBs, repeaters, and MVIDs, andprovide application software upgrades to the communication devices(e.g., PLBs, MVIDs (if necessary), repeaters, and other devices). ThePLS, by collecting electric power distribution information andinterfacing with utilities' back-end computer systems may provideenhanced distribution services such as automated meter reading, outagedetection, load balancing, distribution automation, Volt/Volt-AmpReactance (Volt/VAr) management, and other similar functions. The PLSalso may be connected to one or more APs 100 directly or through theInternet and therefore can communicate with any of the PLBs, repeaters,user devices, and other devices through the respective AP 100.

FIG. 4 illustrates example underground PLCS subnets that employ anembodiment of the present invention. In FIG. 4 each distributiontransformer is indicated by small square box and labeled DT. Referringto network 1, a MVID 300 is installed at two distribution transformersand a PLB 400 is installed at the remaining distribution transformers.For ease of illustration, the PLB 400 and MVIDs 300 in FIG. 4 are notshown separately from the DTs. In network 1, each PLB 400 is incommunication with the closest MVID 300 via the MV power line with whichit is communicatively coupled and provides communications to thecustomer premises via the LV power lines. Thus, the PLBs 400 arecommunicatively coupled to the MV power line and the LV power lines. ThePLB 400 may communicate with the MVID 300 directly, or the data from thePLB 400 may be repeated (e.g., demodulated, source decoded, channeldecoded, error decoded, decrypted. and then encrypted, error encoded,channel encoded, source encoded and modulated) and/or amplified by oneor more of the PLBs 400 between the PLB 400 and the MVID.

The MVIDs 300 may be configured to communicate upstream via a wirelesscommunications link, twisted pair, coaxial cable, other conductor, orvia fiber optic link. In this example, the MVIDs 300 of network 1 are incommunication with a wireless repeater, which is in wirelesscommunication with DP 200, which is in communication with the AP 100 viaa fiber optic link. In other embodiments, the link between the DP 200and AP 100 may be wireless as well. One or more wireless repeaters maybe used between the MVIDs 300 and DP 200 and/or between the DP 200 andAP 100 in the embodiments herein. The repeaters may be daisy-chainedtogether for bi-directional communications via time divisionmultiplexing and/or frequency division multiplexing (e.g., a separateupstream and downstream frequency band) and may use any suitablelicensed or unlicensed bands. Such frequencies may include the much used2.4 GHz, 5 GHz, 24 GHz, and/or 60 GHz wireless bands, for example.Protocols (and therefore frequency bands) used may comprise 802.11a, b,or g, 802.16, and/or 802.21. Thus, the MVID 300 may comprise an antennathat is attached to a tower, transformer enclosure, or other structurethat facilitates wireless communications.

Network 3 includes three DTs with two having a PLB 400. Each PLB 400 isconfigured to communicate with the MVID 300 of that network. The MVID300 of network 3 is in communication with its DP 200 via a fiber opticlink and wireless link as shown.

In networks 1 and 3, the PLBs 400 communicate with user devices in thecustomer premises via the low voltage power lines or, alternately, via awireless link.

In this embodiment, the PLBs 400 provide communication services for theusers, which services may include security management, routing ofInternet protocol (IP) packets, filtering data, access control, servicelevel monitoring, signal processing and modulation/demodulation ofsignals transmitted over the power lines.

At the user end of the PLCS, data flow originates from a user device,which may provide the data to a power line modem (PLM), which iswell-known in the art.

Various electrical circuits within the customer's premises distributepower and data signals within the customer premises. The customer drawspower on demand by plugging a device into a power outlet. In a similarmanner, the customer may plug the PLM into a power outlet to digitallyconnect user devices to communicate data signals carried by the powerwiring. The PLM thus serves as an interface for user devices to accessthe PLCS. The PLM can have a variety of interfaces for customer dataappliances. For example, a PLM may include a RJ-11 Plain Old TelephoneService (POTS) connector, an RS-232 connector, a USB connector, a 10Base-T connector, RJ-45 connector, and the like. In this manner, acustomer may connect a variety of user devices to the PLCS. Further,multiple PLMs may be plugged into power outlets throughout the customerpremises, with each PLM communicating over the same wiring internal tothe customer premises.

The user device connected to the PLM may be any device capable ofsupplying data for transmission (or for receiving such data) including,but not limited to a computer, a telephone, a telephone answeringmachine, a fax, a digital cable box (e.g., for processing digital audioand video, which may then be supplied to a conventional television andfor transmitting requests for video programming), a video game, astereo, a videophone, a television (which may be a digital television),a video recording device, a home network device, a utility meter, orother device. The PLM transmits the data received from the user devicethrough the customer LV power line to a PLB 400 and provides datareceived from the LV power line to the user device. The PLM also may beintegrated with the user device, which may be a computer. In addition,the functions of the PLM may be integrated into a smart utility metersuch as a gas meter, electric meter, water meter, or other utility meterto thereby provide automated meter reading (AMR) and control.

The PLB 400 typically transmits the data to the MVID, which, in turn,transmits the data to the DP 200, which transmits the data to the AP100. The AP 100 then transmits the data to the appropriate destination,which may be a network destination (such as an Internet address) inwhich case the packets are transmitted to, and pass through, numerousrouters (herein routers are meant to include both network routers andswitches) in order to arrive at the desired destination.

System

Referring to FIG. 5, one example of an embodiment of the system of thepresent invention includes an aggregation point 100 including a cablemodem termination system (CMTS) 110 and an opticalmultiplexer/demultiplexer system. As shown, the aggregation point 100that may be co-located with a point of presence (POP). The aggregationpoint 100 may be in communication with one or more distribution points200 via one or more fiber optic cables 140. In other embodiments, thislink may be a wireless link, a T1 link, a coaxial cable, or any othersuitable link. Each distribution point 200 may be in communication withone or more MVIDs 300 via one or more fiber optic conductors 240. EachMVID 300 may be in communication with one or more power line bridges 400via the URD medium voltage power line(s). The PLBs 400 may be incommunication with one or more user devices that reside in the customerpremises via the low voltage power lines or via a wireless link.

In this embodiment, a Frequency Division Multiplexed (FDM) channel planmay be used for allocating multiple downstream and multiple upstreamcommunication channels. Upstream channels also may be multiplexed in thetime domain (Time Division Multiple Access or TDMA) to accommodate thelarge number of PLBs 400 that may exist in large neighborhoods ordaisy-chained MVIDs 300. For example, the PLBs 400 coupled to a URD MVcable may be configured to transmit to an MVID 300 using time divisionmultiplexing, but in the same frequency channel (which may be differentthan the downstream frequency channel). Other embodiments may use otherschemes, such as purely FDM for upstream channels, or Code DivisionMultiple Access (CDMA) which may include Synchronous CDMA (SDMA), orTime Division SCDMA (TD-SCDMA).

In this embodiment, the downstream channels (e.g., as transmitted fromthe MVID 300, amplified by the PLBs 400, and repeated by any repeaters)may be approximately six megahertz (6 MHz) wide. Three such channels maybe used between 30 MHz and 50 MHz on the URD power lines, which has beenfound to be less noisy than frequencies below 30 MHz. In addition, thisfrequency band may be orthogonal from the frequency band (e.g., theHomePlug frequency band) used to communicate over the LV power lineswith the user devices in the customer premises in this embodiment.Consequently, any communications signals that unintentionally bleedthrough the transformer (either from the LV side to the MV or from theMV side to the LV side) will not interfere with communications.

The downstream communications may be 256 Quadrature Amplitude Modulation(QAM) or 64 QAM, Quadrature Phase Shift Keying (QPSK), Binary PhaseShift Keying (BPSK), or any other appropriate modulation format, wherespectrally efficient formats are preferred. In the case of 256 QAM, thecommunications may have 8 bits per symbol while if 64 QAM is used, thecommunications may have 6 bits per symbol. In each case, thecommunications may use differential encoding and have a symbol rate ofmore than 5 MBaud.

Upstream communications such as those transmitted by the PLBs 400 towardthe MVID 300, may be both FDM and TDMA or FDM and SCDMA or simply SCDMA.Many of the communications parameters of the PLBs 400 are configuredunder the direction of the CMTS 110 via the MAC layer controlspecification. Most of these parameters are normally negotiated betweenCMTS 110 and the PLB MV modem (which may be a cable modem). In oneembodiment, a first upstream channel has a bandwidth of approximately1.6 MHz and may employ any of QPSK, 16 QAM, or 64 QAM. Thecommunications may employ differential encoding and have a symbol rateof 1.28 MBaud. For QPSK communications may be at two bits per symbol,for 16 QAM four bits per symbol, and for 64 QAM six bits per symbol maybe used.

A second and third upstream channel may also be 1.6 MHz wide, oralternately, may be 800 KHz wide with each having a symbol rate of 640KBaud (and otherwise having the parameters listed above for the firstupstream channel).

Depending on the layout of the network, the system may employ oneupstream and one downstream channel for each URD MV cable. In otherimplementations, such as where more than one channel is needed due tocapacity or other reasons, two, three, or more channels (upstream and/ordownstream) may be used for communications over one URD MV cable. Aswill be evident to those skilled in the art, the MVIDs 300 may need tocommunicate data in all of the channels, while the PLBs may need tocommunicate data in all, or some subset, of the communication channels.In this embodiment, the channels (frequencies) for communications andamplification by the PLBs may be remotely controlled via a command fromthe PLS. There need not be the same number of upstream and downstreamchannels. Other embodiments of the present invention may use more orfewer channels and/or completely different communications schemes.

Aggregation Point

Referring to FIGS. 5 and 6, this example embodiment includes anaggregation point 100 that includes a CMTS 110 having a plurality ofports. The CMTS 110 may be a large CMTS or a plurality of smaller CMTSs.As is known to those skilled in the art, the output of a CMTS typicallyis a radio frequency electrical signal. The CMTS 110 also may serve as amaster controller, providing instructions and granting requests to/fromdownstream devices (DPs 200, MVIDs 300, and PLBs 400). Such commandstypically relate to the physical layer and may comply with MAC layercontrol specification of DOCSIS (Data Over Cable System InterfaceSpecification) (e.g., DOCSIS 2.0). In other words, the commands andstatus requests transmitted to the network elements, and responsesthereto, may substantially or fully comply with the format and protocol(e.g., the bit sequence) defined by the DOCSIS specification.

Each port of the CMTS 110 may be communicatively coupled to anElectrical-to-Optical converter (EO converter) 130. This embodimentincludes a plurality of groups of EO converters 130, with each group ofEO converters 130 communicating with an opticalmultiplexer/demultiplexer 135. All of the EO converters 130 in a groupmay communicate with the multiplexer/demultiplexer 135 via a differentwavelength. The Optical Multiplexer/Demultiplexer 135 may include anArrayed Waveguide Grating (AWG) or Thin Film Filter (TFF) and/or FiberBragg Grating (FBG). Each optical multiplexer/demultiplexer 135 receivesoptical signals from its corresponding EO converters 130 and multiplexesthe signals onto one or more optical conductors 140. In this exampleembodiment, the optical multiplexer/demultiplexer 135 transmits to eachdistribution point 200 on one fiber conductor and receives from eachdistribution point on another optical fiber conductor. The output of theoptical multiplexer 135 may be amplified prior to transmission onto theoptical conductor. Thus, the downstream (DS) transmission from theoptical multiplexer/demultiplexer 135 (or optical amplifier (OA)) maycomprise a plurality of different wavelengths and the communications maybe amplitude modulated and be a dense wave division multiplexed (DWDM)or coarse wave division multiplexed (CWDM) signal. In other embodiments,this link may be digital. In addition, or instead of wave divisionmultiplexing, additional fiber conductors may be used. Thus, the AP 100may include one or more ports for fiber optic communications and couldinclude one or more fiber optic transceivers—although the transceiver(s)may not necessarily communicate over the same fiber optic conductor.

In the upstream direction (i.e., data transmitted from the DP 200 to theAP 100), data is received by the optical multiplexer/demultiplexer 135and demultiplexed (based on the wavelengths of the signals in thisembodiment). The demultiplexed outputs are communicated to therespective OE converter 130 which then converts the optical signal to anelectrical signal. The output of the OE converter 130 is provided to theCMTS 110, which communicates the signal via the POP to the appropriatenetwork such as the Internet or a voice network.

While this figure discloses only two distribution points 200, any numberof distribution points 200 may be communicatively coupled to theaggregation point 100 provided the aggregation point 100 is suitable tohandle the information capacity. In addition, while the AP 100 of FIGS.5 and 6 utilize optical links to communicate with their DPs 200, othersystems may in addition to, or instead, employ wireless, coaxial, T1,SONET, or any other suitable link, and therefore, will have theappropriate transceiver for providing such communications.

Distribution Point

The distribution point 200 receives the downstream optical signals(e.g., via an optical conductor 140) from the opticalmultiplexer/demultiplexer 135 of the aggregation point 100. Thedistribution point 200 includes a multiplexer/demultiplexer 235, thatoperates substantially similar to the multiplexer/demultiplexer 135 ofthe aggregation point 100. The DP 200 also may include a plurality ofdownstream ports. Thus, the DP 200 may include one or more ports forfiber optic communications and could include one or more fiber optictransceivers—although the transceiver(s) may not necessarily communicateover the same fiber optic conductor.

The multiplexer/demultiplexer 235 of the DP 200 may demultiplex thereceived optical signals (based on wavelength in this embodiment) andoutput each demultiplexed signal via one of its downstream ports. Inthis example embodiment, each downstream port is communicatively coupledto a MVID 300 via one or more fiber optic conductors 240. In addition,the DP 200 may convert the optical signals to optical digital signalsand modulate the signals onto an optical carrier of the same, ordifferent, wavelength. In this embodiment, each downstream port of theDP 200 communicates with the associated MVID 300 via a differentwavelength, and therefore, the system uses wavelength divisionmultiplexing.

The DP 200 also may include a cable modem (e.g., a CableLabs CertifiedCable Modem) and central processing unit in order to receive and processcontrol commands and status requests. Control and status of DPs may beaccomplished by means of an in-band channel. Such signals may betransmitted from the AP 100 (e.g., from the CMTS 110 therein and may beDOCSIS commands) or PLS.

Upstream optical signals may be received from each MVID 300 via aseparate port. Each upstream optical signal may be multiplexed by theDP's multiplexer/demultiplexer and communicated upstream to theaggregation point 100. The signals received from the MVID 300 by the DP200 may be converted to optical digital signals and modulated onto anoptical carrier of the same, or different, wavelength.

MVID

Each MVID 300 receives the downstream data signals from the DP 200 andconverts the optical signals to electrical signals. The communicationsbetween the DP 200 and the MVIDs 300 (and between the AP 100 and DPs200) may be amplitude modulated (AM) fiber optic signals. At the MVID300, DOCSIS compliant RF signals (e.g., optical signals) may beconverted to a frequency channel plan which is more compatible with theURD MV cable/coupler power line communications infrastructure. Thus, onefunction of the MVID 300 may be to shift the channels from their CATVspectral assignments to those in the URD channel plan. The MVID 300 alsomay serve as the optical/electrical interface device by convertingdownstream AM fiber signals into electrical RF signals and vice-versafor upstream signals.

As shown in FIG. 6, the MVID 300 may be communicatively coupled to oneor more URD medium voltage power lines for example, at a riser pole(where the underground power line traverses up a pole to connect to anoverhead power line) or at an URD transformer such as the firsttransformer connected to the riser pole in the URD system. In thisexample, the MVID 300 is coupled to all three phases (phase A, B, and C)of the three phase URD power distribution system. As shown, the MVID 300may be in communication with one or more PLBs 400 via each URD MV powerline. The URD transformers, and their associated PLBs, are connectedtogether by a length of URD cable that typically may be up to 1000 feetin length, but may sometimes be longer.

In some embodiments, the MVID 300 may perform routing and transmit thedata signals over the appropriate MV power line. Alternately, and as inthis example embodiment, the MVID 300 simply converts the incomingsignal from an optical signal (or a wireless signal in alternateembodiment) to an electrical signal and transmits the electrical signalsdown all (or some) of the URD MV power lines. As will be evident tothose skilled in the art, the less processing that the MVID 300 (andother network elements) perform, the faster the network will communicatedata (i.e., the system will have less latency), which is important forvoice, video, and other latency sensitive applications.

PLB

The PLB 400 may include a processing section and a through section. EachPLB 400 receives the downstream data signals via the MV power line. Inthis example embodiment, each PLB 400 receives all the data transmittedfrom the MVID 300 on the MV power line to which the PLB 400 isconnected. The processing section of the PLB 400 demodulates all thedata signals to determine whether the data should be processed by thePLB 400 (e.g. as a command) or transmitted to the user devices on thePLB's LV subnet. If the data signals include appropriate addressinformation (as discussed in detail below), the PLB 400 may process thedata or transmit the data via the LV subnet to be received by a userdevice in a customer premises (not shown). If the data signals do notinclude the appropriate address information, the data signals may beignored. In addition to demodulating and processing the data, thethrough section of the PLB 400 may amplify, filter and transmit all thedata signals it receives for reception by the downstream PLBs 400.

Upstream data signals received by the PLBs 400 on the MV power line maybe amplified, filtered and transmitted by the through section of the PLB400 toward the MVID 300. Thus, each PLB 400 may include a bi-directionalamplifier to amplify all the downstream (and upstream) data signals thatmay be attenuated as they propagate through the URD MV cable. In thisembodiment, there is no need to demodulate and process the upstreamdata. Other embodiments, which may operate in a noise environment, mayprovide demodulation and modulation of MV power line upstream data atthe PLB to thereby repeat the data.

The PLB 400 also receives upstream data via the LV power line from theuser device(s) at the customer premises (not shown). This data may beprocessed and transmitted upstream by the processing section of the PLB400 to the MVID 300. In other embodiments, the PLB 400 may communicatewith devices at the customer premises via another link such as a fiberoptic cable, a coaxial cable, a twisted pair, or a wireless link. (e.g.,an IEEE 802.11).

System Variations

While the above described embodiment includes a DP 200, otherembodiments may not include a DP 200. For example, FIG. 7 depicts a PLCSthat does not employ a DP 200. The embodiment depicted in FIG. 7 may besuitable for single phase URD power distribution segments. Theaggregation point 100 communicates directly with a plurality of MVIDs300, which may be located in the pit of, or adjacent to, a URDtransformer (instead of at the riser pole) such as the first URDtransformer or the URD transformer that is most directly connected tothe pole riser. In other words, the MVIDs 300 in the embodiment may beco-located with a PLB 400 and may communicate with the adjacent PLB 400over a conventional telecommunications medium such as a coaxial cable orEthernet cable.

The aggregation point 100 of FIG. 7 remains substantially similar to theaggregation point 100 of FIG. 5 except that there may be nomultiplexer/demultiplexer present. Instead, the optical output of eachOE converter 130 of the AP 100 may communicate with an associated MVID300 via an upstream optical fiber conductor 140 a and a downstreamoptical fiber conductor 140 b using amplitude modulated fiber opticsignals.

FIG. 8 depicts another example system in which a DP 200 is not presentand in which the AP 100 is providing communications for three differentMVIDs 300. The MVIDs 300 may be located in the pit of, or adjacent to, aURD transformer (instead of at the riser pole) such as the first URDtransformer or the URD transformer that is most directly connected tothe pole riser. In other words, the MVIDs 300 in the embodiment may beco-located with a PLB 400 and may communicate over a conventionaltelecommunications medium such as a coaxial cable or Ethernet cable. Theembodiment depicted in FIG. 8 may be suitable for single phase URD powerdistribution segments. In this example embodiment, a signal EO converter130 provides communications to multiple MVIDs 300. As shown in FIG. 8,the downstream fiber optic link 140 b between the AP 100 and the MVIDs300 may be connected to splitters that split the signals so that allthree MVIDs 300 receive all downstream communications from the AP 100.The upstream links 140 a of the MVIDs 300 are chained together as shownand, therefore, are all combined on one fiber optic cable. Specifically,the upstream link 140 a from MVID 300 a is coupled to MVID 300 b wherethe signals of MVID 300 a and 300 b may be combined (electrically). Theupstream link from MVID 300 b is coupled to MVID 300 c where the datasignals from MVID 300 b (which may include signals from MVID 300 a and300 b) and MVID 300 c may be combined (electrically). The combinedsignals are then communicated to the EO converter 130 of the AP 100,where they may be converted to electrical signals and demodulated. Thefiber optic signals employed in this embodiment may be amplitudemodulated fiber optic signals.

FIG. 9 depicts a DP 200 that communicates with its associated MVIDs 300in substantially the same manner as the AP 100 of FIG. 8. The embodimentdepicted in FIG. 9 also may be suitable for single or multi-phase URDpower distribution segments. The MVIDs 300 may be located in the pit of,or adjacent to, a URD transformer (instead of at the riser pole) such asat the first URD transformer or the URD transformer that is mostdirectly connected to the pole riser. Thus, the MVIDs 300 in theembodiment may be co-located with a PLB 400 and may communicate withthat PLB 400 over a conventional telecommunications medium such as acoaxial cable or Ethernet cable. Data communicated between the MVIDs 300and other downstream PLBs 400 may traverse through (and be amplified by)the PLB 400 with which the MVID 300 is co-located.

The DP 200 of FIG. 9 includes an analog-to-digital converter (ADC) forthe upstream communications from the MVIDs 300. The ADC converts theanalog optical signals from the MVIDs 300 (i.e., the amplitude modulatedoptical signals) to digital optical signals for upstream transmissionsto the AP 100. As will be evident to those skilled in the art, the otherDPs 200 and MVIDs 300 disclosed herein might also include an ADC andoperate accordingly. As shown in FIG. 9, the downstream fiber optic link140 b between the DP 200 and the MVIDs 300 may be connected to splittersthat split the signals so that all three MVIDs 300 receive alldownstream communications form the DP 200 and, if desirable, maytransmit all received data downstream to the PLBs 400. The upstreamlinks 140 a of the MVIDs 300 may be chained together as shown anddiscussed above and, therefore, may be combined on one fiber optic cableby the MVID 300 with which the DP 200 is most directly communicativelycoupled.

MVID

FIG. 10 depicts an example embodiment of a MVID 300 that is coupled toone MV power line for communications to one or more PLBs. The MVID 300may be installed at, or on, a utility pole at a pole riser. The MVID 300also may be communicatively coupled to fiber optic conductors 140 forcommunications with an upstream device such as a DP 200 or AP 100. Suchfiber optic signals may include modulated fiber optic signals, which maybe amplitude modulated (as in the embodiment) or digitally modulated(i.e., be digital optical signals). In other embodiments, the MVID 300,which may be mounted at the riser pole, may include a wirelesstransceiver for communication with the DP 200 or AP 100 in the licensedor unlicensed frequency bands. As shown in FIG. 10, downstream datasignals are received via a fiber optic cable 140 b and converted from anoptical to an electrical signal via an OE converter 330 a. The output ofthe OE converter 330 a is supplied to a tuner 331 or other band passfilter that may filter out all but the frequency band containing thedesired information. The output of the tuner 331 may be supplied to apre-emphasis filter. The pre-emphasis filter 332 may attenuate thesignal so that certain frequencies may be transmitted with more powerthan other frequencies. Because higher frequencies may be attenuatedmore than lower frequencies by the URD cable, the pre-emphasis filter332 may attenuate the lower frequencies more than the higher frequencies(e.g., providing a slope across the frequency band) to compensate forthe anticipated loss of the URD cable. Thus, the pre-emphasized signalmay be received at the other end of the URD cable as a more flat signal(e.g., having more uniform power spectrum) across the carrier frequencyband than if the signal had not been pre-emphasized. In otherembodiments, pre-emphasis may be performed via a pre-emphasis amplifierin addition to, or instead of, the pre-emphasis filter.

The output of the pre-emphasis filter 332 is supplied to a lineamplifier 333. The signal amplified by the line amplifier 333 issupplied to a diplexer 334, which is communicatively coupled to coupler420. An alternate embodiment, could use an a power splitter or adirectional coupler or any device configured to separate the downstreamand upstream signals (e.g., via frequency for FDM), which couples thedownstream frequencies to the MV coupler and onto the URD MV power linefor reception by the PLBs 400 instead of a diplexer. It is worth notingthat this example embodiment of the MVID 300 does not route ordemodulate and modulate the downstream signals and, therefore, has alower latency than might be provided from a MVID 300 that does route,demodulate and/or modulate the signals (which would also be within thescope of the present invention).

The upstream data signals are coupled from the MV power line to thediplexer 334 (or any other device that can separate the downstream andupstream signals) via the MV coupler 420. The diplexer 334 couples theupstream frequencies to the low noise amplifier (LNA) 340, which may beconnected to a band pass filter (or image filter) 341. The amplified andfiltered signals are supplied to a first intermediate frequency (IF)converter 342 (e.g., a mixer that receives an input from the localoscillator (Lo) synthesizer 345 to shift the frequency) and then to anIF filter 343. Thus, the amplified and filtered signal is frequencyshifted, filtered, and then supplied to a second frequency converter 344(e.g., a mixer that receives an input from the local oscillator (Lo)synthesizer 345 to shift the frequency) which converts the data signalsto the appropriate frequency for upstream transmission.

The output of the second frequency converter 344 is supplied to aprogrammable gain amplifier (PGA) 346. Data signals from downstreamMVIDs 300 are received by EO converter 330 b and converted to electricalsignals. The amplified output of the PGA 346 may be combined by combiner347 with the upstream data signals of the other downstream MVIDs 300(that converted to electrical signals by EO converter 330 b), and thenprovided to the upstream OE converter 330 c for conversion to an opticalsignal for transmission upstream to a DP 200 or AP 100 (as depicted byMVID 300 c shown in FIGS. 8 and 9 or the MVIDs shown in FIG. 7) or toanother MVID 300 (as depicted by MVIDs 300 a and 300 b of FIGS. 8 and9).

The MVID 300 also may include a cable modem (e.g., a CableLabs CertifiedCable Modem) and central processing unit in order to receive and processcontrol commands and status requests. Control and status of MVIDs (andPLBs) may be accomplished by means of an in-band channel. Such signalsmay be transmitted from the AP 100 (e.g., the CMTS 110 therein in thecase of DOCSIS commands) or PLS.

In this embodiment the communications (both upstream and downstream)that are upstream from the MVID 300 (e.g., between the MVID 300 and DP200 and between the DP 200 and AP 100) may employ a substantially DOCSIS(e.g. DOCSIS 2.0) (Data Over Cable System Interface Specification)compliant protocol. format, and physical layer. This is indicated by thevertical dotted line in FIGS. 7, 8, and 9. While the protocol andphysical layer may be substantially DOCSIS 2.0 compliant, the mediums(e.g., fiber) and hardware (e.g., DP 200) may not be consistent with aconventional DOCSIS system. Of course, variations of DOCSIS andprotocols and physical layers that are not similar to DOCSIS may besuitable as well in some embodiments. For example, a systemsubstantially compliant with a Digital Audio Visual Council (DAVIC)specification alternately may be employed (i.e., protocol, format,commands and/or status requests thereof).

In addition, in this embodiment the communications (both upstream anddownstream) that are downstream from the MVID 300 (e.g., between theMVID 300 and PLBs) may employ a substantially DOCSIS (Data Over CableSystem Interface Specification) compliant protocol and physical layerand a frequency scheme that is consistent with DOCSIS.

This example embodiment uses a first frequency band for upstreamcommunications from the PLBs 400 to their MVID 300 and a secondfrequency band for upstream communications from the MVIDs 300 to theirupstream devices (DP 200 or AP 100). Thus, frequency translation isrequired by MVID 300 in this example. For example, the first frequencyband (between the PLBs 400 and the MVID 300) may be from approximately54 MHz to 100 MHz and the second frequency band (between the MVIDs 300and the DP 200 or AP 100) may be from 5 MHz to 50 MHz. In this exampleembodiment, the downstream communications to the MVID 300 (from a DP 200or AP 100) may use the same frequency as the downstream communicationsfrom the MVID 300 to its PLBs 400. Consequently, frequency translationis not required in this example embodiment. In other embodiments thedownstream channels may be frequency translated (i.e., frequencyshifted) by MVID 300.

FIG. 11 depicts another example embodiment of a MVID 300, which also maybe installed at, or on, a utility pole at a pole riser. The MVID 300also may be communicatively coupled to fiber optic conductors forcommunications with an upstream device such as a DP 200 or AP 100. Suchfiber optic signals may comprise amplitude modulated fiber opticsignals, but could also be digital optical signals. In this exampleembodiment, the downstream communications to the MVID 300 (from a DP 200or AP 100) use a different frequency than the downstream communicationsfrom the MVID 300 to its PLBs 400. In addition, the upstreamcommunications from the PLBs 400 to the MVID 300 employ differentfrequencies than the upstream communications from the MVID 300 to itsupstream device (DP 200 or AP 100). Consequently, frequency translationmay be required in both the upstream and downstream directions.

Thus, downstream data received by the MVID 300 from its upstream devicewill be converted to an electrical signal by the OE converter 330 a andconverted to an IF frequency by the first IF converter 350 (e.g., amixer that receives an input from the Lo synthesizer 351 to shift thefrequency). The output of the converter 350 may be band pass filtered byband pass filter 352 and supplied to a second frequency converter 353,which converts the signals to the frequencies used on the MV power line.The output of the second converter 353 is image filtered by image filter354 and amplified by a line amplifier 355. The amplified signal issupplied to a diplexer 334 that couples the downstream frequencies tothe MV power line via the MV coupler 420 and circuit protectioncircuitry 356.

Upstream data signals received from the PLBs 400 are coupled from the MVcoupler 420 to the LNA 357 by the diplexer 334 and circuit protectioncircuitry 356. The LNA 357 amplifies the signals, which are provided toa bandpass filter 358, which filters for the band of frequencies usedfor upstream communications on the URD MV power line. The output of thefilter 358 is supplied to a PGA 359, which amplifies the signal. Theamplified signals are then supplied to a frequency converter 360 thatconverts the frequency band received to the frequency band used forupstream communications. Data signals from downstream MVIDs 300 arereceived by EO converter 330 b and converted to electrical signals. Theoutput of the frequency converter 360 may pass through an imagerejection filter (not shown) before being combined with the upstreamdata signals of other MVIDs 300 (if any) by combiner 361 before beingconverted to amplitude modulated optical signals by the OE converter 330c and transmitted to the upstream device (DP 200 or AP 100).

It is worth noting that these example embodiments of the MVID 300 maynot employ a modulator or demodulator for upstream or downstreamcommunications, thereby ensuring low latency through the MVID 300.

This embodiment of the MVID 300 also may include a cable modem (e.g., aCableLabs Certified Cable Modem) and central processing unit in order toreceive and process control commands and status requests as discussedabove.

PLB

FIG. 12 depicts a portion of an example embodiment of a PLB 400. Inparticular, FIG. 12 depicts the through portion of the PLB 400, whichamplifies both the upstream and downstream communications frequencies.As will be discussed in more detail below, in this embodiment,communications via the MV power line use separate frequencies forupstream transmissions (from the PLB 400 to the MVID 300) and downstreamtransmissions (from the MVID 300 to the PLBs 400). Thus, referring tothe left side of FIG. 12, the downstream frequency band is coupled to afirst diplexer 410 a (or any other device capable of isolating thedownstream signals from the upstream signals) from the MV power line viathe first MV coupler 420 a. The first diplexer 410 a couples thedownstream frequencies to the LNA 411, which amplifies the signals thatare then supplied to a bandpass filter 412. The bandpass filter filtersfor the downstream frequencies. The output of the bandpass filter 412(which may be programmable by controller) is supplied to both ademodulator 480 and an automatic level control (ALC) amplifier 413. Theoutput of the ALC amplifier 413 is supplied to a second diplexer 410 b(or any other device capable of combining the downstream and upstreamsignals), which couples the amplified data signals of the downstreamfrequencies to the MV power line via the second MV coupler 420 b. Thedemodulator 480 and other process related portions of the PLB 400 arediscussed below.

Referring to the right side of FIG. 12, the upstream frequency band iscoupled to the second diplexer 410 b (or any other device capable ofisolating the upstream signals from the downstream signals) from the MVpower line via the second MV coupler 420 b. The second diplexer 410 bcouples the data communicated in the upstream frequency band(s) to theupstream low noise amplifier 415, which amplifies the upstream signals.Thus, each PLB 400 may be equipped with bi-directional linearamplifiers. A form of “soft” automatic gain control (AGC) may be used,providing gain/power level control for downstream and upstreamdirections at each amplifier PLB 400. Control of this system function isunder the direction of the CMTS 110 via a downstream control channel.Repeaters may also be deployed to regenerate the modulated signal onextremely long/lossy channels.

The output of the upstream low noise amplifier 415 is combined with theamplified output (amplified by amplifier 417) of the modulator 481(e.g., via time division multiplexing, code division multiplexing,and/or as specified by DOCSIS 2.0) via combiner 416. Instead ofamplifier 417, the output power of the modulator 417 could be set high(or simply be higher than permitted by federal regulations) in whichcase amplifier 417 may be replaced with an adjustable attenuator. TheDOCSIS 2.0 specification is hereby incorporated by reference in itsentirety. The amplified signal may be supplied to the first diplexer 410a (or any other device capable of combining the upstream and downstreamsignals), which couples the upstream frequencies to the MV power linevia the first MV coupler 420 a for reception by the MVID 300.

Thus, the through section of the PLB 400 amplifies both the upstream anddownstream data signals (based on their frequency) without demodulatingand modulating the data, thereby reducing latency (compared to if thesignal was demodulated and modulated) and increasing the distance ofcommunications via the amplification. It is has been found that the URDMV power line cables are very lossy at frequencies used to providebroadband communications. In addition, government regulations limit theamount of power that can be used to transmit such signals. Consequently,in comparison to other communications mediums, the transmitted signalswill travel only relatively short distance on the URD MV power lines.Other embodiments of the PLB 400 may include demodulating andre-modulating the data signals to permit communicating long distancesover the URD MV cables. However, the increased latency of the PLB 400may reduce the quality of the time sensitive applications (e.g., voiceand video delivery) to a point where such applications are precluded. Incontrast, the example embodiment of the PLB 400 disclosed providesamplification of the signal in both directions without a significantlatency increase.

After transmission of the data signals toward a PLB 400 (e.g., fromanother PLB or the MVID), the data signals will be attenuated by the URDcable, the MV couplers (e.g., the MV couplers on each end of the URDcable), and other power distribution elements (e.g., taps). Theattenuation (or loss) caused by the URD MV cable is related to itslength. While the loss of the MV coupler may be substantiallypredetermined, the distance to the PLB, and length of the URD cable,typically will vary between URD transformers. In other words, thechannel loss between each PLB is not the same because the distancebetween each PLB, and length of the URD cable, is not the same.Consequently, even if the data signals are transmitted at the same powerlevel toward each PLB, the data signals may be received at a differentpower levels at each PLB 400 due to the variances in the loss of thechannel associated with each PLB 400 (i.e., variances in the lengths ofthe URD cables that the data signals must traverse to reach each PLB400).

The transmit level may be defined as the average RF power spectraldensity (PSD) at the center frequency of the channel transmitted duringthe data symbols of a burst, assuming equally likely QAM symbols, andmeasured at the output of the PLB 400. The maximum output power levels(for both the transmissions from the PLB modem and PLB amplifiers) andassociated radiated emissions must always be less than or equal to theappropriate Federal Communications Commission's Part 15 limits (i.e.,≦P_(FCC) _(—) _(Limit)).

As discussed below, the MV coupler provides isolation to therebyattenuate signals that might otherwise traverse through the URDtransformer where they could be undesirably received by the MV coupleron the other side of the transformer and create a feedback loop. Thus,the transmit levels may also (or instead) be limited by the isolationprovided by the MV couplers. In summary, there is a ceiling to theoutput power levels of the PLB's bi-directional amplifiers (i.e.,amplification power) and modem (i.e., transmit power).

As discussed, for data signals transmitted at the same power levels, thepower levels of those signals when received may vary from PLB to PLB.For those PLBs receiving data signals via a short URD cable, the datasignals typically will be received at higher power levels than thosePLBs receiving data signals via a long URD cable. Consequently, anamplifier providing the same amplification at each PLB may not suffice,because the higher power level signals may be amplified above the FCCpower limits (or above the isolation limits of the MV couplers) and/orthe lower power level data signals may not be amplified enough to allowthe signals to be reliably received by the next PLB 400 (or the MVID300).

In some embodiments, an automated gain control or automatic levelcontrol amplifier may be used. However, transmissions in the upstreamdirection are often bursts, which do not allow enough time for an AGC orALC amplifier to adjust the amplification. Consequently, the presentinvention provides a method of gain control to compensate for receivingsignals of varying power levels for upstream communications. Fordownstream communications, in which transmissions are more constant, anALC amplifier may be used to adjust the amplification.

Gain Alignment is the task of adjusting the gains of each PLB 400upstream amplifier to achieve a desired overall cascaded gain. Inaddition, the output of the PLB 400 transmitter (e.g., transmitting datafrom the PLB such as user data) may also be adjusted accordingly. Inthis embodiment, the desirable overall cascaded gain may be ≧60 dB (<60dB loss) from the furthest PLB 400 to the MVID 300 input. A net loss maybe acceptable and may result from the accumulation of long single-URDspans that attenuate the signal more than a single upstream amplifier ata PLB 400 is capable of compensating. The 60 dB max cascaded loss isdetermined by the minimum carrier-to-noise (C/N) objective of thisexample embodiment.

While the upstream amplifiers, like the downstream amplifiers, may begain limited (e.g., due to limited isolation between URD MV couplers),the MVID 300 gain is not limited in this manner, and may be capable ofmuch higher gains, which will be used for signal level alignment.

In an example system shown in FIG. 9, there are four spans, S₀, S₁, S₂,and S₃. Each span will consist of two URD MV couplers and a length ofURD Cable. Other spans, such as those that traverse tap-pits may havethree or more MV Couplers and two or more cable spans. The variables S₀. . . S₃ represent the total equivalent power loss in dB for each span.

There are also four gain stages, A_(MVID), A₁, A₂, and A₃. Gains A₁, A₂,and A₃ represent the gain in PLBs 400 a, b, and c, respectively. Thefourth gain stage, A₄, is not used in this case, as PLB 400 d is thelast PLB 400 in the cascade. A_(MVID) is the amplifier incorporated inthe MVID 300 c, and is not gain limited as in the PLBs 400. A_(MVID), A₁. . . A₃ are gains expressed in dB. These gains could be used, forexample, to determine the amplification of adjustable (or programmable)upstream amplifier 415 in FIG. 12 for example.

P₁, P₂, P₃, and P₄ are the output power spectral densities of the PLB'stransmitter (e.g., data transmitted from the MV modem) for PLB 400 a, b,c, and d, respectively. They are measured in units of dBm/Hz and arecontrolled in the PLBs 400 by a software programmableamplifier/attenuator, which the level of the output of the transmitter(or cable modem (e.g., a CableLabs Certified Cable Modem) in thisexample). As discussed, these power levels must always be ≦P_(FCC) _(—)_(Limit). These power outputs, for example, could be used to set theamplification of adjustable (or programmable) amplifier 417 of FIG. 12,or an attenuator may be replace amplifier 417 in some embodiments.

The gain and transmit PSD settings for any PLB upstreamamplifier/transmitter may be determined from the following rules:

P_(n)≦P_(FCC) _(—) _(Limit) (expressed in dBm/Hz)

A_(n)≦A_(max) (maximum upstream gain)

No amplifier output level can exceed P_(FCC) _(—) _(Limit)

In this example embodiment, the following system design objectives maybe: (1) the desired cascaded system gain, including A_(MVID), is 0 dB;(2) the entire PLB-MVID cascaded gain is bounded by: −60 dB≦A_(total)≦0dB; and (3) any intermediate cumulative loss be ≦50 dB.

For a cascaded chain of N PLBs the following formulas may be used tocompute the upstream amplifier gains and maximum upstream transmitterpower spectral densities.

The upstream gain of the n^(th) PLB 400 is:A _(n) =[S _(n)+Σ(S _(k) −A _(k)), A _(max)]_(min)

The maximum transmit PSD for the n^(th) PLB 400 is:P _(n) =P _(FCC) _(—) _(Limit)−Σ(S _(k) −A _(k))

Based on these equations, the gains may be computed starting at thefurthest PLB 400 from the MVID 300, PLB_(N-1) followed by PLB_(N-2) andso on until reaching the MVID 300. Also, the output power level P_(n) ofPLB_(n) is computed after figuring the gain A_(n) of PLB_(n).

For the example of FIG. 9, the gains and transmission powers may becomputed as follows:P₄=P_(FCC) _(—) _(Limit)A ₃ =[S ₃+(S ₄ −A ₄), A _(max)]_(min) (S ₄ and A ₄ are 0, end of line) P₃ =P _(FCC) _(—) _(Limit)−(S ₃ −A ₃)

Using A₃ from above, A₂ and P₂ can be calculated below as:A ₂ =[S ₂+(S ₃ −A ₃)+(S ₄ −A ₄), A _(max)]_(min)P ₂ =P _(FCC) _(—) _(Limit)−(S ₂ −A ₂)−(S ₃ −A ₃)

Using A₂ and A₃ from above, A₁ and P₁ can be calculated below as:A ₁ =[S ₁+(S ₂ −A ₂)+(S ₃ −A ₃)+(S ₄ −A ₄), A _(max)]_(min)P ₁ =P _(FCC) _(—) _(Limit)−(S ₁ −A ₁)−(S ₂ −A ₂)−(S ₃ −A ₃)

Using A₁, A₂ and A₃ from above, A_(MVID) can be calculated below as:A _(MVID) =[S ₀+(S ₁ −A ₁)+(S ₂ −A ₂)+(S ₃ −A ₃)+(S ₄ −A ₄), A_(max)]_(min)

The output power of the amplifier or transmitter may be adjusted up ordown or, alternately, the output power may be set at a fixedpredetermined level and attenuated to provide the desired output power.

The loss of a span (S_(n)) may be determined in any suitable manner. Forexample, the PLB 400 may transmit a tone, or range of tones (e.g. acrossall or a portion of the communications channel), at a predeterminedpower level (e.g. at the P_(FCC) _(—) _(Limit) or MV coupler limit).Based on the power level(s) of the received signal, the receiving device(e.g., a PLB 400 or MVID 300) may then determine the loss of the span.After determining the loss of the span, the software program stored inthe memory of the controller of the PLB 400 may then execute thealgorithms above in order to set the output gain and power of theamplifier and transmitter. The tone(s) may be transmitted atinstallation, periodically, when the error rate exceeds a predeterminedthreshold, or upon receiving a command from the CMTS 110 (of the AP 100)or PLS.

Upstream data from the user devices will be supplied to the throughsection via the modulator 480 as discussed below. In this embodiment,all the downstream data from the URD cable may be filtered, anddemodulated for processing by the PLB 400. If the data signals aresuccessfully demodulated, they may be transmitted to the appropriateuser device.

As shown in FIG. 13, in addition to the through section shown in FIG.12, the PLB 400 also includes a processing section that includes a MVmodem 480, a controller/router 470, a LV power line coupler 440, a LVsignal conditioner 460, and a LV modem 450.

The PLB 400 is controlled by a programmable processor and associatedperipheral circuitry, which form part of the controller 470. Thecontroller 470 includes memory that stores, among other things, programcode, which controls the operation of the processor. The controller andmodem may be integrated.

The router forms part of the controller 470 and performs routingfunctions. The router may perform routing functions using layer 3 data(e.g., IP addresses), layer 2 data (e.g., MAC addresses), or acombination of layer 2 and layer 3 data (e.g., a combination of MAC andIP addresses). In addition to routing, the controller 470 may performother functions including controlling the operation of the modems. Amore complete description of the controller 470 and its functionality isdescribed below.

The controller 470 may receive and respond to commands originating fromthe PLS. The MV modem 480, which may be a cable modem (e.g., a CableLabsCertified Cable Modem), may receive and respond to DOCSIS commands thatmay originate from the CMTS 110 of the AP 100. For example, the CMTS maytransmit a command (e.g., using the format and protocol defined by aDOCSIS specification) directing the MV modem 480 of the PLB 400 to use aparticular upstream channel (e.g., frequency band). In response to thecommand, the MV modem 480 may send and an acknowledgment (and/orotherwise respond according to the DOCSIS specification) and use thedesignated upstream channel for future communications. The MV modem 480may receive and process, and respond as appropriate, any of the DOCSIScommands that may be useful for the application. In some embodiments,the MV modem 480 need not be able to process every DOCSIS commanddefined in the DOCSIS specification. The commands processed by thecontroller 470 are described below. Communications between the PLS andthe controller 470 of the PLB 400 may employ Simple Network ManagementProtocol (SNMP). In addition, the PLS may transmit a command to thecontroller 470 of the PLB 400 instructing the controller 470 to controlor modify the operation of the MV modem 480. For example, the PLS maytransmit an instruction to the controller 470 to cause the MV modem 480to transmit the tone(s) described above in order to set the output gainand transmission power levels.

As discussed, this embodiment of the present invention providesbi-directional communications to thereby provide a first communicationspath from the LV power line to the MV power line and a second path fromthe MV power line to the LV power line. For ease of understanding, theprocessing, and functional components of a communication path from theLV power line to the MV power line (the LV to MV path) will be describedfirst. Subsequently, the processing and functional components of thecommunication path from the MV power line to the LV power line (the MVto LV path) will be described.

As will be evident to those skilled in the art, the two paths arelogical paths. The LV to MV path and the MV to LV path may be separatephysical electrical paths at certain functional blocks and may be thesame physical path in other functional blocks. However, otherembodiments of the present invention may provide for a completely, orsubstantially complete, separate physical path for the LV to MV and theMV to LV paths.

LV Power Line to MV Power Line Path

In the United States, the LV power line typically includes a neutralconductor and two conductors carrying current (“energized”) conductors.In the United States, the two energized conductors typically carry about120V alternating current (AC) at a frequency of 60 Hz and are 180degrees out of phase with each other. The present invention is suitablefor LV power line cables having conductors that are spaced apart or thatare coupled together (e.g., in a twisted pair or via the conductorinsulation).

LV Coupler

The LV power line coupler 440 couples data to and from the LV power lineand may include a transducer. The coupler 440 also may couple power fromthe LV power line, which is used to power at least a portion of the PLB400. In this embodiment, the electronics of much of the PLB 400 ishoused in an enclosure with first and second PLB 400 cables extendingfrom the enclosure. The first PLB 400 cable includes a twisted pair ofconductors including a signal conductor and neutral conductor. The firstconductor of the first PLB 400 cable is connected to one of theenergized LV conductors extending from the transformer and the secondconductor of the first PLB 400 cable is connected to the neutralconductor extending from the transformer. In this embodiment, clampingthe PLB 400 conductors to the LV power line conductors makes theconnection.

The second PLB 400 cable extending from the enclosure is also a twistedpair comprised of a first and second conductor. The first conductor ofthe second PLB 400 cable is connected to the neutral conductor extendingfrom the transformer and the second conductor of the second PLB 400cable is connected to the second (other) energized LV conductorextending from the transformer.

The third PLB 400 cable is a ground conductor that may be connected toan earth ground, which typically is an earth ground conductor thatconnects the transformer housing to a ground rod. The neutral conductorof the LV power line may also be connected to the earth ground of thepower line system (by the electric power company). However, there may bean intrinsic RF impedance between the PLB 400 ground conductorconnection and the LV neutral conductor connections of the PLB 400(i.e., the second conductor of the first PLB 400 cable and the firstconductor of the second PLB 400 cable). Additionally, it may bedesirable to add an RF impedance (e.g., an RF choke) between theconnections.

In other embodiments, the LV coupler 410 may include a transducer andmay be an inductive coupler such as toroid coupling transformer or acapacitive coupler, for coupling data to and/or from the LV power lineand/or for coupling power from the LV power line.

In this embodiment, the signals entering the PLB 400 via the first andsecond PLB 400 cables (hereinafter the first signal and second signalrespectively) are processed with conventional transient protectioncircuitry, which is well-known to those skilled in the art. Next, thefirst signal and second signal are processed with voltage translationcircuitry. The data signals in this embodiment, which are in the 4.5 to21 MHz HomePlug 1.0 band, “ride on” (i.e., are additive of) the lowfrequency power signal (the 120V 60 Hz voltage signal). Consequently, inthis embodiment, it is desirable to remove the low frequency powersignal, but to keep the data signals for processing, which isaccomplished by the voltage translation circuitry. The voltagetranslation circuitry may include a high pass filter to remove the lowfrequency power signal and may also (or instead) include otherconventional voltage translation circuitry.

Next, the first and second signals may be processed with impedancetranslation circuitry, which is well-known in the art. In thisembodiment, it is desirable to substantially match the impedance of theLV power line. One method of matching the impedance of the LV power lineis to separately terminate the PLB 400 LV conductors of the first andsecond PLB 400 cables through a termination resistor to ground. Thevalue of the termination resistor may be selected to match thecharacteristic impedance of the LV power line.

The electronics of the PLB 400 may be powered by power received from theLV power line. Thus, this embodiment of the PLB 400 includes a powersupply for powering much of the PLB 400 electronics. The power supplymay include its own transient protection circuitry, which may be inaddition to, or instead of, the transient protection circuitry thatprocesses the data signals described above. Thus, the power supply mayreceive power from the PLB 400 LV conductor of the first (or second) PLB400 cable after the power signal passes through the transient protectioncircuitry.

In addition to the power supply, the PLB 400 may include a batterybackup for operating the PLB 400 during power outages. Thus, a backuppower system (which may include a battery) may allow the device todetect a power outage and communicate information relating to the outageto the utility company and/or PLS. In practice, information of theoutage may be transmitted to the PLS, which communicates the location,time, and/or other information of the outage to the power utility (e.g.,the utility's computer system). The backup power system also may allowthe PLB 400 to communicate certain data packets during a power outage.For example, during an outage, the PLB 400 may be programmed tocommunicate all voice data, only emergency voice transmissions (e.g.,phone calls dialed to 911), or a notice of the power outage.

LV Signal Conditioner

The data signals are received via the transmit/receive circuitry,examples of which (as well as other circuitry) are shown in FIGS. 14 band c and are discussed below. As shown in FIG. 14 a, after passingthrough the transmit/receive circuitry and LV transmit/receive switch426 (which would be in receive mode) the first signal (comprising datasignals from the PLB 400 LV conductor of the first cable) is supplied toa first filter 421 a that has a pass band of approximately 4.0 to 10MHz. The second signal (comprising data signals from the PLB 400 LVconductor of the second PLB 400 cable) is supplied to a second filter421 b that has a pass band of approximately 10-21 MHz. Each of thesefilters 421 provides pass band filtering and may also provideanti-aliasing filtering for their respective frequency bands, and noisefiltering.

The outputs of the first and second filters 421 a-b are supplied to afirst amplifier 422 a and second amplifier 422 b, respectively. Theoutputs of the first and second amplifiers 422 a-b are coupled to afirst feedback device 423 a and a second feedback device 423 b,respectively. Each feedback device 423 measures the power over time andsupplies the power measurement to the controller 470. Based on the powermeasurement, the controller 470 increases, decreases, or leaves the gainof the associated amplifiers the same to provide automatic gain control(AGC). The outputs of the first and second amplifiers 422 are alsosupplied to a summation device 424 that sums the two pass band,amplified signals to provide a single data signal.

Thus, the gain of the second amplifier 422 b, which receives signals inthe 10-21 MHz band, may be greater (or may be dynamically made greater)than the gain of the first amplifier 422 a, which receives signals inthe 4.5 to 10 MHz band. The higher gain of the second amplifier filter422 b can thus compensate for the greater loss of the transmissionchannel at the higher frequencies.

In this embodiment, the amplification by the amplifiers 422 isaccomplished by amplifying the signal a first predetermined amount,which may be the same or different (e.g., such as proportional to theanticipated loss of the channel) for each amplifier. The amplifiedsignal is then attenuated so that the resultant amplified andsubsequently attenuated signal is at the appropriate amplification withrespect to the original signal, which may be determined by controller470 from information received by the feedback devices 423. The feedbackdevice 423 may be implemented with suitable feedback architecture,well-known to those skilled in the art. For example, the feedbackdevices 423 may use both hardware (such as feedback that may be providedby an analog to digital converter) and software (such as in modifyingthe reference voltage supplied to an operational amplifier that isimplementing the amplifier 422).

Other embodiments may not include filtering the inputs of the two PLB400 LV conductors at separate pass bands and separately amplifying thefiltered signals. Instead, the signal may be filtered and amplifiedacross the entire LV power line communication pass band (e.g., from 4.5to 21 MHz). Similarly, while this embodiment divides the LV power linecommunication channel into two bands (for filtering, amplifying andsumming), other embodiments may similarly divide the LV power linecommunication channel into three, four, five or more bands (forfiltering, amplifying and summing).

LV Modem

The LV modem 450 may include a modulator and demodulator. The LV modem450 also may include one or more additional functional submodules suchas an Analog-to-Digital Converter (ADC), Digital-to-Analog Converter(DAC), a memory, source encoder/decoder, error encoder/decoder, channelencoder/decoder, MAC (Media Access Control) controller, encryptionmodule, and decryption module. These functional submodules may beomitted in some embodiments, may be integrated into a modem integratedcircuit (chip or chip set), or may be peripheral to a modem chip. In thepresent example embodiment, the LV modem 450 is formed, at least inpart, by part number INT5130, which is an integrated power linetransceiver circuit incorporating most of the above-identifiedsubmodules, and which is manufactured by Intellon, Inc. of Ocala, Fla.Thus, the modem may be a Homeplug compatible (1.0 or AV) modem.

The incoming signal is supplied to an ADC to convert the incoming analogsignal to a digital signal. The digital signal is then demodulated. TheLV modem 450 then provides decryption, source decoding, error decoding,channel decoding, and media access control (MAC) all of which are knownin the art and, therefore, not explained in detail here.

With respect to MAC, however, the LV modem 450 may examine informationin the packet to determine whether the packet should be ignored orpassed to the router. For example, the modem 450 may compare thedestination MAC address of the packet with the MAC address of the LVmodem 450 (which is stored in the memory of the LV modem 450). If thereis a match, the LV modem 450 removes the MAC header of the packet andpasses the packet to the router. If there is not a match, the packet maybe ignored.

Router

The data packets from the LV modem 450 may be supplied to the router,which forms part of the controller 470. The router performsprioritization, filtering, packet routing, access control, andencryption. The router of this example embodiment of the presentinvention uses a table (e.g., a routing table) and programmed routingrules stored in memory to determine the next destination of a datapacket. The table is a collection of information and may includeinformation relating to which interface (e.g., LV or MV) leads toparticular groups of addresses (such as the addresses of the userdevices connected to the customer LV power lines), priorities forconnections to be used, and rules for handling both routine and specialcases of traffic (such as voice packets and/or control packets).

The router will detect routing information, such as the destinationaddress (e.g., the destination IP address) and/or other packetinformation (such as information identifying the packet as voice data),and match that routing information with rules (e.g., address rules) inthe table. The rules may indicate that packets in a particular group ofaddresses should be transmitted in a specific direction such as throughthe LV power line (e.g., if the packet was received from the MV powerline and the destination IP address corresponds to a user deviceconnected to the LV power line), repeated on the MV line (e.g., if thePLB 400 is acting as a repeater), or be ignored (e.g., if the addressdoes not correspond to a user device connected to the LV power line orto the PLB 400 itself).

As an example, the table may include information such as the IPaddresses (and potentially the MAC addresses) of the user devices on thePLB's LV subnet, the MAC addresses of the power line modems on the PLB'sLV subnet, the MV subnet mask (which may include the MAC address and/orIP address of the PLBs 400, DP 200 (if any) or AP 100 (if any)), and theIP address of the LV modem 450 and MV modem 480. Based on thedestination IP address of the packet (e.g., an IP address), the routermay pass the packet to the MV modem 480 for transmission on the MV powerline. Alternately, if the IP destination address of the packet matchesthe IP address of the PLB, the PLB 400 may process the packet as arequest for data.

In other instances, such as if the user device is not provisioned andregistered, the router may prevent packets from being transmitted to anydestination other than a DNS server or registration server of the PLCSoperator. In addition, if the user device is not registered, the routermay replace any request for a web page received from that user devicewith a request for a web page on the registration server (the address ofwhich is stored in the memory of the router) of the operator of thePLCS.

The router may also prioritize transmission of packets. For example,data packets determined to be voice packets may be given higher priorityfor transmission through the PLB 400 than data packets so as to reducedelays and improve the voice connection experienced by the user. Routingand/or prioritization may be based on IP addresses, MAC addresses,subscription level, or a combination thereof (e.g., the MAC address ofthe power line modem or IP address of the user device).

MV Modem

Similar to the LV modem 450, the MV modem 480 receives data from therouter and includes a modulator and demodulator. In addition, the MVmodem 280 also may include one or more additional functional submodulessuch as an ADC, DAC, memory, source encoder/decoder, errorencoder/decoder, channel encoder/decoder, MAC controller, encryptionmodule, and decryption module. These functional submodules may beomitted in some embodiments, may be integrated into a modem integratedcircuit (chip or chip set), or may be peripheral to a modem chip. Inthis example embodiment the MV modem may be comprised of a DOCSIScompliant modem (e.g., DOCSIS 2.0), which may be a cable modem (e.g., aCableLabs Certified Cable Modem).

The modem may employ QAM digital modulation such as 16, 64, and/or256-QAM. Different digital modulation formats may be used for downstreamand upstream channels. Downstream channels may use 64 or 256 QAM, whileupstream channels may use QPSK, or 16 or 64 QAM. In one embodiment, andas discussed above, three downstream channels may be used, with eachhaving a bandwidth of approximately 6 MHz and located in the 30-50 MHzband. The band has been found to have less noise from consumerappliances and less interference from higher frequency television bands.One channel may centered at approximately 32.7 MHz which as been foundto have a lower cable loss than some other frequencies. The upstreamchannels, which may comprise three or more channels, may be in theavailable spectrum between 72 MHz and 76 MHz.

In another embodiment, the MV modem 480 is formed, at least in part, bypart number INT5130, which is an integrated power line transceivercircuit incorporating most of the identified submodules and which ismanufactured by Intellon, Inc. of Ocala, Fla.

The incoming signal from the router (i.e., the controller) is suppliedto the MV modem 480, which may provide MAC processing, for example, byadding a MAC header that includes the MAC address of the MV modem 480 asthe source address and the MAC address of the upstream device as thedestination MAC address. In addition, the MV modem 480 also may providechannel encoding, source encoding, error encoding, and encryption. Thedata is then modulated and provided to the DAC to convert the digitaldata to an analog signal.

First MV Signal Conditioner

The modulated analog signal from the MV modem 480 is provided to firstMV signal conditioner (not shown), which may provide filtering(anti-alias, noise, and/or band pass filtering) and amplification. Inaddition, the MV signal conditioner 260 may provide frequencytranslation. In this embodiment, translation of the frequency isaccomplished through the use of a local oscillator and a conversionmixer. This method and other methods of frequency translation are wellknown in the art and, therefore, not described in detail.

As is known in the art, frequency translation may result in a first andsecond image of the original frequency although in some instances, suchas in the present embodiment, only one of the two images is desired.Thus, the frequency translation circuitry may include an image rejectionfilter to filter out the undesired image leaving only the desiredfrequency bandwidth, which in this embodiment is the higher frequencyband of the MV power line.

The output of the MV signal conditioning circuitry is supplied to thethrough portion of the PLB 400 shown in FIG. 12. In summary, the outputof the MV signal conditioning circuitry may be supplied to an amplifierand combiner and then coupled onto the URD MF power line to conductionto the MVID 300 (perhaps via other PLB 400 through portions).

MV Power Coupler Line

The coupling device couples the data onto the URD MV power line. Thecoupling device may be inductive, capacitive, conductive, a combinationthereof, or any suitable device for communicating data signals to and/orfrom the MV power line. In this example embodiment, the MV coupler is athree port device, with a first port coupling data to the PLB 400, asecond port coupling power signals to or from the distributiontransformer (while impeding or filtering data signals), and a third portcoupling both data and power to the URD MV power line. Thus, the firstport may include a high pass filter to permit the data signals to pass,but to impede the lower frequency power signals. The second port maycomprise a low pass filter (or high frequency attenuator) to allow thelow frequency power signals to pass substantially unimpeded. Thus, thetwo URD MV power cables connected to the transformer may be consideredseparate communication channels. One example of such a coupler isdescribed in U.S. application Ser. No. 10/947,929 filed Sep. 23, 2004,entitled “Power Line Coupling Device and Method of Using the Same,”Attorney Docket CRNT-0216, which is hereby incorporated by reference inits entirety.

Path from MV Power Line to LV Power Line

As discussed the MV power line coupler also receives data signals fromthe MV power line via a coupling device, which may take the form of anyof those coupling devices described above. The data signals from the MVcoupler may pass through transient suppression circuitry, and impedancetranslation circuitry. In addition, the signals traverse the diplexer410 a, the LNA, the bandpass filter, and the splitter of the thrusection of the PLB 400 to be received by the MV modem 480 as shown inFIG. 12.

MV Modem

The MV modem 480 and LV modem 450 provide a bi-directional path and formpart of the MV to LV path and the LV to MV path. The components of theMV modem 480 have been described above in the context of the LV to MVpath and are therefore not repeated here. The incoming signal may besupplied to the ADC to convert the incoming analog signal to a digitalsignal. The digital signal is then demodulated. The modem then providesdecryption, source decoding, error decoding, and channel decoding all ofwhich are known in the art and, therefore, not explained in detail here.

The MV modem 480 also provides MAC processing through the use of MACaddresses. In one embodiment employing the present invention, the MACaddress is used to direct data packets to the appropriate device. TheMAC addresses may provide a unique identifier for one or more of thedevices on the PLC network including, for example, user devices, PLBs,power line modems, repeaters (if any), MVIDs 300, DPs 200, and APs 100.However, in some implementation, some of these network elements may nothave an address (e.g., a MVID).

The routing upstream device (e.g., a MVID, DP 200 or AP 100) maydetermine the MAC address of the MV modem 480 of the PLB 400 servicingthe user device. The information for making this determination may bestored in a table in the memory of the upstream device. The upstreamdevice may remove the MAC header of the packet and add a new header thatincludes the MAC address of the transmitting device (as the sourceaddress) and the MAC address of the PLB 400 (the destination address)—ormore specifically, the MAC address of the MV modem 280 of thedestination PLB.

Thus, in this embodiment, packets destined for a user device on a LVsubnet of a PLB 400 (or to the PLB) are addressed to the MAC address ofthe MV modem 480 of the PLB 400 and may include additional information(e.g., the destination IP address of the user device) for routing thepacket to devices on the PLB's LV subnet.

If the destination MAC address of the received packet does not match theMAC address of the MV modem 480, the packet may be discarded (ignored).If the destination MAC address of the received packet does match the MACaddress of the MV modem 480, the MAC header may be removed from thepacket and the packet is supplied to the router for further processing.

There may be a different MAC sublayer for each physical device type suchas for user devices and PLCS network elements (which may include anysubset of devices such as MVIDs 300, PLBs 400, repeaters, DPs 200, andaggregation points 100).

Router

As discussed above, upon reception of a data packet, the MV modem 480 ofa PLB 400 will determine if the destination MAC address of the packetmatches the MAC address of the MV modem 480 and, if there is a match,the packet is passed to the router. If there is no match, the packet isdiscarded.

In this embodiment, the router analyzes packets having a destination IPaddress to determine the destination of the packet which may be a userdevice or the PLB 400 itself. This analysis includes comparing theinformation in the packet (e.g., a destination IP address) withinformation stored in memory, which may include the IP addresses of theuser devices on the PLB 400 LV subnet. If a match is found, the routerroutes the packet through to the LV modem 450 for transmission on the LVpower line. If the destination IP address matches the IP address of thePLB, the packet is processed as a command or data intended for the PLB400 (e.g., by the Command Processing software described below) and maynot be passed to the LV modem 450.

The term “router” is sometimes used to refer to a device that routesdata at the IP layer (e.g., using IP addresses). The term “switch” issometimes used to refer to a device that routes at the MAC layer (e.g.,using MAC addresses). Herein, however, the terms “router”, “routing”,“routing functions” and the like are meant to include both routing atthe IP layer and MAC layer. Consequently, the router of the presentinvention may use MAC addresses instead of, or in addition to, IPaddresses to perform routing functions.

For many networks, the MAC address of a network device will be differentfrom the IP address. Transmission Control Protocol (TCP)/IP includes afacility referred to as the Address Resolution Protocol (ARP) thatpermits the creation of a table that maps IP addresses to MAC addresses.The table is sometimes referred to as the ARP cache. Thus, the routermay use the ARP cache or other information stored in memory to determineIP addresses based on MAC addresses (and/or vice versa). In other words,the ARP cache and/or other information may be used with information inthe data packet (such as the destination IP address) to determine therouting of a packet (e.g., to determine the MAC address of the powerline modem communicating with the user device having the destination IPaddress).

In an alternate embodiment using IP address to route data packets, allpackets received by the MV modem 480 may be supplied to the router. Therouter may determine whether the packet includes a destination IPaddress that corresponds to a device on the PLB's LV subnet (e.g., anaddress corresponding to a user device address or the PLB's address).Specifically, upon determining the destination IP address of an incomingpacket, the router may compare the identified destination address withthe addresses of the devices on the subnet, which are stored in memory.If there is a match between the destination address and the IP addressof a user device stored in memory, the data is routed to the LV powerline for transmission to the user device. If there is a match betweenthe destination address and the IP address of the PLB 400 stored inmemory, the data packet is processed as a command or informationdestined for the PLB.

In addition, the router may also compare the destination address withthe IP address of the upstream device, other PLBs. If there is no matchbetween the destination address and an IP address stored in memory, thepacket is discarded (ignored).

According to any of these router embodiments, if the data is addressedto an address on the PLB's LV, the router may perform any or all ofprioritization, packet routing, access control, filtering, andencryption.

As discussed, the router of this example embodiment of the presentinvention may use a routing table to determine the destination of a datapacket. Based on information in the routing table and possibly elsewherein memory, the router routes the packets. For example, voice packets maybe given higher priority than data packets so as to reduce delays andimprove the voice connection experienced by the user. The routersupplies data packets intended for transmission along the LV power lineto the LV modem 450.

LV Modem

The functional components of the LV Modem 450 have been described abovein the context of the LV to MV path and, therefore, are not repeatedhere. After receiving the data packet from the router, the LV modem 450provides MAC processing, which may comprise adding a MAC header thatincludes the source MAC address (which may be the MAC address of the LVmodem 450) and the destination MAC address (which may be the MAC addressof the power line modem corresponding to the user device identified bythe destination IP address of the packet).

To determine the MAC address of the power line modem that providescommunications for the user device identified by the destination IPaddress of the packet, the LV modem 450 first determines if thedestination IP address of the packet is an IP address stored in itsmemory (e.g., stored in its bridging table). If the IP address is storedin memory, the LV modem 450 retrieves the MAC address for communicatingwith the destination IP address (e.g., the MAC address of the power linemodem) from memory, which will also be stored therein. If the IP addressis not stored in memory, the LV modem 450 transmits a request to all thedevices to which it is coupled via the low voltage power line (e.g., allthe power line modems). The request is a request for the MAC address forcommunicating with the destination IP address of the packet. The device(e.g., the power line modem) that has the MAC address for communicatingwith the destination IP address will respond by providing its MACaddress. The LV modem 450 stores the received MAC address and the IPaddress for which the MAC address provides communications in its memory(e.g., in its bridging table). The LV modem 450 then adds the receivedMAC address as the destination MAC address for the packet.

The packet is then channel encoded, source encoded, error encoded, andencrypted. The data is then modulated and provided to the DAC to convertthe digital data to an analog signal.

LV Signal Conditioner

The output of the LV modem 450 is provided to the LV signal conditioner460, which conditions the signal for transmission. Knowing (ordetermining) the frequency response (or loss) of the LV power linetransmission channel allows the device to predistort or pre-emphasizesignals prior to transmission to compensate for anticipated losses atcertain frequencies or frequency ranges. During and/or prior totransmission, the amount of amplification necessary for particularfrequency ranges may be periodically determined according to methodsknown in the art to provide dynamic predistortion (i.e., changing theamount of amplification of all or portions (e.g., frequencies orfrequency ranges) of the signal over time of the transmitted signal. Thedetermination of the desired amount of amplification may, for example,be determined and/or relate to the amount of amplification performed byamplifiers in the LV to MV path. Alternately, the amplification may becharacteristic for a particular type of channel (e.g., overhead orunderground), or measured for a channel, and the predistortion thus maybe fixed (preprogrammed and/or hardwired into the device).

In this embodiment, signals at higher frequencies are amplified morethan signals at lower frequencies to compensate for the anticipatedgreater loss at the higher frequencies. As shown in FIG. 14 a, thesignal to be transmitted is amplified with an amplifier that providesgreater amplification at higher frequencies of the 4.5 to 21 MHz band.Such amplifiers are well-known to those skilled in the art. Theamplifier may have a transfer function substantially inverse to thefrequency response of the LV transmission channel. Once amplified andfiltered, the signal is conducted through switch 426 to the LV powerline coupler 440 for transmission on the energized LV conductors of theLV power line. Of course, in alternate embodiments the transmission maynot be predistorted and may be filtered and amplified substantially thesame across the transmission channel.

FIG. 14 b illustrates the transmit circuit used to drive the data signal(indicated by Vs). Components to the left of the dashed line in FIG. 14b may be inside the PLB 400 enclosure and those to the right may beoutside the PLB 400 enclosure. The transmit circuit of this embodimentincludes a transformer that drives the two conductor pairs 436 and 437.Each conductor pair 436, 437 is coupled to ground by impedance Z3, whichmay be resistive. In addition, each conductor 436 a,b and 437 a,bincludes a series impedance Z1, which may be capacitive (e.g., providinga high pass filter) and/or resistive.

As discussed, the first and second PLB 400 cables 436, 437 are eachcomprised of a twisted pair of conductors 436 a,b and 437 a,b. As willbe evident to those skilled in the art, each twisted pair cable 436, 437will have an impedance (determined by the geometry of the cable) asrepresented by Z2 in FIG. 14 b. This impedance Z2 may be modeled by aresistive component and an inductive component. The inductive componentalso may cause coupling between the two twisted conductors of eachcable.

LV Power Line Coupler

In addition to the above, the LV power line coupler 410 may include theimpedance matching circuitry and transient protection circuitry. Thecoupler 410 couples the data signal onto the LV power line as describedabove for reception by a user device communicatively coupled to the LVpower line via a power line modem.

After the LV energized conductors enter the customer premises, typicallyonly one LV energized conductor will be present at each wall socketwhere a power line modem might be installed (e.g., plugged in). Giventhis fact regarding the internal customer premises wiring, there is noway to know to which LV energized conductor the power line modem (anduser device) will be connected. In addition, the subscriber may move thepower line modem and user device to another socket to access the PLCSand the new socket may be coupled to the second (different) LV energizedconductor. Given these facts, the network designer must supplycommunications on both LV energized conductors and, therefore, would bemotivated to simultaneously transmit the PLC RF data signal on each LVenergized conductor referenced to the neutral conductor. However, incomparison to transmitting the RF data signals on both energizedconductors referenced to the neutral, the following method of providingcommunications on the LV energized has been found to provide improvedperformance.

As shown in FIG. 14 b, the first PLB 400 cable 436 is coupled to the LVpower line so that the data signal is applied to the first LV energizedconductor referenced to the LV neutral conductor. The second PLB 400cable 437 is coupled to the LV power line so that the data signal (Vs)is applied to the neutral conductor referenced to the second LVenergized conductor. As a result, the data signal is applied to thefirst and second LV energized conductors differentially. In other words,with reference to the neutral conductor, the voltage signal(representing the data) on the second LV energized conductor is equal inmagnitude and opposite in polarity of the voltage on the first LVenergized conductor. Similarly, the current flow representing the dataon the second LV energized conductor will be the opposite of the currentflow on the first LV energized conductor in magnitude and direction. Ithas been found that differentially driving the LV energized conductorsas described provides significant performance improvements over methods,which may result from reduced reflections, improved signal propagation,and impedance matching among other things. It is worth noting thetransmit circuit of this and the following embodiments may transmit datasignals with multiple carriers (e.g., eighty or more) such as with usingan Orthogonal Frequency Division Multiplex (OFDM) modulation scheme.

FIG. 14 c illustrates another embodiment of a transmit circuit fortransmitting the data signal. Components to the left of the dashed linein FIG. 14 c may be inside the PLB 400 enclosure and those to the rightmay be outside the PLB 400 enclosure. The transmit circuit of thisembodiment is comprised of a transformer that drives one conductor pair436, which traverse through a common mode choke. The common mode chokeprovides a very low impedance to differential currents in the twoconductors 436 a,b, but provides a significant or high impedance tocommon mode currents (i.e., currents traveling in the same directionsuch as in or out). The two conductors 436 a,b may also be coupled toground by an impedance Z3, which may be a resistive impedance. Inaddition, each conductor 436 a, b includes a series impedance Z1, whichmay be a capacitive impedance, or other high pass filter component(s),for impeding the 60 Hz power signal and permitting the RF data signal topass unimpeded. Such impedances may be on either side of the common modechoke, but are preferably on the LV power line side of the choke.

In either embodiment, each conductor may also include a surge protectioncircuit, which in FIG. 14 c are shown as S1 and S2. Finally, the cable436 may be comprised of a twisted pair of conductors between the PLB 400enclosure and LV power line. As will be evident to those skilled in theart, the twisted pair cable 436 may have an impedance (determined by thegeometry of the cable) as represented by Z2. This impedance Z2 may bemodeled by a resistive component and an inductive component. Theinductive component also may cause coupling between the two twistedwired conductors.

While not shown in the figures, the transmit circuit of eitherembodiment may also include a fuse in series with each conductor and avoltage limiting device, such as a pair of oppositely disposed zenerdiodes, coupled between the pair of conductors and may be locatedbetween the common mode choke and the transformer. Finally, one of theconductors of the PLB 400 cable(s) 436 or 437 may used to supply powerto the power supply of the PLB 400 to power the PLB.

It is worth noting that these embodiments of the present invention drivethe first and second LV energized conductors differentially to transmitthe data signal (e.g., using OFDM). However, the power line modemtransmits data signals from the customer premises to the PLB 400 byapplying the data signal to one conductor (e.g., one energizedconductor) referenced to the other conductor such as a ground and/orneutral.

While in this embodiment the two energized conductors are opposite inmagnitude, other embodiments may phase shift the data signal on oneconductor (relative to the data signal on the other conductor) byforty-five degrees, ninety degrees, one hundred twenty degrees, onehundred eighty degrees, or some other value, in addition to or insteadof differentially driving the two conductors.

Controller

As discussed, the controller 470 includes the hardware and software formanaging communications and control of the PLB. In this embodiment, thecontroller 470 may include an IDT 32334 RISC microprocessor [NEED NEWPROCESSOR] for running the embedded application software and alsoincludes flash memory for storing the boot code, device data andconfiguration information (serial number, MAC addresses, subnet mask,and other information), the application software, routing table, and thestatistical and measured data. This memory includes the program codestored therein for operating the processor to perform the routingfunctions described herein. Other processors may be used as well. Inanother embodiment, the controller may be formed by the centralprocessing unit of the cable modem.

This embodiment of the controller also includes random access memory(RAM) for running the application software and temporary storage of dataand data packets. This embodiment of the controller 470 also includes anAnalog-to-Digital Converter (ADC) for taking various measurements, whichmay include measuring the temperature inside the PLB 400 (through atemperature sensor such as a varistor or thermistor), for taking powerquality measurements, detecting power outages, measuring the outputs offeedback devices, and others. The embodiment also includes a “watchdog”timer for resetting the device should a hardware glitch or softwareproblem prevent proper operation to continue.

This embodiment of the controller 470 also includes an Ethernet adapter,an optional on-board MAC and physical (PHY) layer Ethernet chipset thatcan be used for converting peripheral component interconnect (PCI) toEthernet signals for communicating with the backhaul side of the PLB.Thus, an RJ45 connector may provide a port for a wireless transceiver(which may be a 802.11 compliant transceiver) for communicatingwirelessly.

The PLB 400 also may have a debug port, such as a debug port that can beused to connect serially to a portable computer. The debug portpreferably connects to any computer that provides terminal emulation toprint debug information at different verbosity levels and can be used tocontrol the PLB 400 in many respects such as sending commands to extractall statistical, fault, and trend data.

In addition to storing a real-time operating system, the memory ofcontroller 470 of the PLB 400 also includes various program codesections such as a software upgrade handler, software upgrade processingsoftware, the PLS command processing software (which receives commandsfrom the PLS, and processes the commands, and may return a status backto the PLS), the ADC control software, the power quality monitoringsoftware, the error detection and alarm processing software, the datafiltering software, the traffic monitoring software, the network elementprovisioning software, and a dynamic host configuration protocol (DHCP)Server for auto-provisioning user devices (e.g., user computers) andassociated power line modems.

The router in this embodiment is not physically located between the twomodems, but instead all three devices—the router, LV modem 450, and MVmodem 280—are communicatively coupled together via the bus.Consequently, in some instances (e.g., at the occurrence of a particularevent) the router may be programmed to allow the LV modem 450 to passdata directly to the MV modem 280 and vice versa, without performingdata filtering and/or the other functions performed by the router whichare described above.

This embodiment of the PLB 400 may only receive or transmit data overthe LV power line at any one instant. However, as will be evident tothose skilled in the art, the PLB 400 may transmit or receive over theLV power line, while simultaneously transmitting or receiving data overthe MV power line and, depending on the specific implementation, may beable to receive and transmit on the MV side simultaneously (becausethose communications may use different frequency bands). Upstreamcommunications from each PLB 400 may be time division multiplexed, whiledownstream communications may be broadcast (e.g., point to multi-point).

Any suitable frequency scheme may be used for communications over the MVpower line. For example, if only one downstream channel is used (forcommunications from the MVID 300 to the PLBs), the system may use a sixmegahertz (MHz) channel from 29.7 MHz to 35.7 MHz and employ 256 QAM. Ifadditional channels are used, such channels also may be six megahertzand be located between 36.85 MHz to 42.85 MHz and another from 44 MHz to50 MHz. The upstream power line channel may be larger or smaller thanthe downstream channels. For example, the upstream communications (fromPLBs 400 to the MVID) may be from 71.965 MHz to 74.835 MHz.

PLS Command Processing Software

The PLS and PLB 400 (or repeater) may communicate with each otherthrough two types of communications: 1) PLS Commands and PLB 400responses, and 2) PLB 400 Alerts and Alarms. TCP packets are used tocommunicate commands and responses. The commands typically are initiatedby the NEM portion of the PLS. Responses sent by the PLB 400 (orrepeater) may be in the form of an acknowledgement (ACK) or negativeacknowledgement (NACK), or a data response depending on the type ofcommand received by the PLB 400 (or repeater).

Commands

The PLS may transmit any number of commands to the PLB 400 to supportsystem control of PLB 400 functionality. As will be evident to thoseskilled in the art, most of these commands are equally applicable forrepeaters. For ease of discussion, however, the description of thecommands will be in the context of a PLB 400 only. These commands mayinclude altering configuration information, synchronizing the time ofthe PLB 400 with that of the PLS, controlling measurement intervals(e.g., voltage measurements of the ADC), requesting measurement or datastatistics, requesting the status of user device activations, andrequesting reset or other system-level commands. Any or all of thesecommands may require a unique response from the PLB, which istransmitted by the PLB 400 (or repeater) and received and stored by thePLS.

Alerts

In addition to commands and responses, the PLB 400 (or repeater) has theability to send Alerts and Alarms to the PLS (the NEM) via User DatagramProtocol (UDP), which does not require an established connection butalso does not guarantee message delivery.

Alerts typically are either warnings or informational messagestransmitted to the NEM in light of events detected or measured by thePLB. Alarms typically are error conditions detected by the PLB. Due tothe fact that UDP messages may not be guaranteed to be delivered to thePLS, the PLB 400 may repeat Alarms and/or Alerts that are criticallyimportant to the operation of the device.

One example of an Alarm is an Out-of-Limit Alarm that indicates that anout-of-limit condition and has been detected at the PLB, which mayindicate a power outage on the LV power line, a temperature measurementinside the PLB 400 is too high, and/or other out-of-limit condition.Information of the Out-of-Limit condition, such as the type of condition(e.g., a LV voltage measurement, a PLB 400 temperature), theOut-of-Limit threshold exceeded, the time of detection, the amount(e.g., over, under, etc.) the out of limit threshold has been exceeded,is stored in the memory of the PLB 400 and may be retrieved by the PLS.

Software Upgrade Handler

The Software Upgrade Handler software may be started by the PLS CommandProcessing software in response to a PLS command. Information needed todownload the upgrade, including for example the remote file name and PLSIP address, may be included in the parameters passed to this softwaremodule (or task) from the Software Command Handler.

Upon startup, this task may open a file transfer program such as TrivialFile Transfer Protocol (TFTP) to provide a connection to the PLS andrequest the file. The requested file is then downloaded to the PLB. Forexample, the PLS may transmit the upgrade through the Internet, throughthe backhaul point 10, through the MV power line to the PLB 400 wherethe upgrade may be stored in a local RAM buffer and validated (e.g.,error checked) while the PLB 400 continues to operate (i.e., continuesto communicate packets to and from power line modems and the backhaulpoint 10). Finally, the task copies the downloaded software into abackup boot page, and transmits an Alert indicating successfulinstallation to the PLS. A separate command transmitted from the PLS,processed by the Command Processing software of the PLB, may make thenewly downloaded and validated program code the primary softwareoperating the PLB. If an error occurs, the PLB 400 issues an Alertindicating the download was not successful.

ADC Scheduler

The ADC Scheduler software, in conjunction with the real-time operatingsystem, creates ADC scheduler tasks to perform ADC sampling according toconfigurable periods for each sample type. Each sample type correspondswith an ADC channel. The ADC Scheduler software creates a schedulingtable in memory with entries for each sampling channel according todefault configurations or commands received from the PLS. The tablecontains timer intervals for the next sample for each ADC channel, whichare monitored by the ADC scheduler.

Based on the measured voltages, the PLS may also determine the locationand/or area of a power outage. Periodically, the PLS may ping each (orsome subset of) network element. The determination of a power outage maybe made by a failure of a network element to respond to the periodicping (or other command or request) transmitted by the PLS. If thenetwork element has an alternate power source such as a battery backup,the network element may transmit a notification of the power outage(e.g., based on a low voltage measurement by the network element).

Based on the network element(s) serial number(s), the PLS can retrievethe network element's physical location (such as its pole number, whichmay be mapped to a longitude and latitude and/or street address) frommemory to determine the location of the power outage. Thus, bydetermining that a number of network elements are not responsive, thePLS may map an area without power. Information of the power outage, suchas the location(s) time, etc., may then be transmitted to the utilitycompany.

ADC Measurement Software

The ADC Measurement Software, in conjunction with the real-timeoperating system, creates ADC measurement tasks that are responsible formonitoring and measuring data accessible through the ADC 330. Eachseparate measurable parameter may have an ADC measurement task. Each ADCmeasurement task may have configurable rates for processing, recording,and reporting for example.

An ADC measurement task may wait on a timer (set by the ADC scheduler).When the timer expires the task may retrieve all new ADC samples forthat measurement type from the sample buffer, which may be one or moresamples. The raw samples are converted into a measurement value. Themeasurement is given the timestamp of the last ADC sample used to makethe measurement. The measurement may require further processing. If themeasurement (or processed measurement) exceeds limit values, an alarmcondition may be generated. Out of limit Alarms may be transmitted tothe PLS and repeated at the report rate until the measurement is backwithin limits. An out of limit recovery Alert may be generated (andtransmitted to the PLS) when the out of limit condition is cleared(i.e., the measured value falls back within limit conditions).

The measurements performed by the ADC 330, each of which has acorresponding ADC measurement task, may include PLB 400 insidetemperature, LV power line voltage, LV power line current (e.g., thevoltage across a resistor), AGC1 (corresponding to Feedback device 423a), and AGC2 (corresponding to Feedback device 423 a) for example.

As discussed, the PLB 400 includes value limits for most of thesemeasurements stored in memory with which the measured value may becompared. If a measurement is below a lower limit or above an upperlimit (or otherwise out of an acceptable range), the PLB 400 maytransmit an Out-of-Limit Alarm, which is received and stored by the PLS.In some instances, one or more measured values are processed to convertthe measured value(s) to a standard or more conventional data value.

The measured data (or measured and processed data) is stored in thememory of the PLB. This memory area contains a circular buffer for eachADC measurement and time stamp. The buffers may be read by the PLSCommand Processing software task in response to a request for ameasurement report. The measurement data may be backed up to flashmemory by the flash store task.

The LV power line voltage measurement may be used to provide variousinformation. For example, the measurement may be used to determine apower outage, or measure the power used by a consumer or by all of theconsumers connected to that distribution transformer. In addition, itmay be used to determine the power quality of the LV power line bymeasuring and processing the measured values over time to providefrequency, harmonic content, and other power line qualitycharacteristics.

Traffic Monitoring Software

The Traffic Monitoring software may collect various data packet trafficstatistics, which may be stored in memory including the amount of data(i.e., packets and/or bytes) communicated (i.e., transmitted andreceived) through the MV power line, and/or through the LV power line;the amount of data (packets and/or bytes) communicated (transmitted andreceived) to and/or from the PLS; the number of Alerts and Alarms sentto the PLS; the number of DHCP requests from user devices; the number offailed user device authentications; the number of failed PLSauthentications; and the number of packets and bytes received and/ortransmitted from/to each user device (or power line modem 50).

Data Filtering Software

The Data Filtering software provides filtering of data packetstransmitted to and/or from a user device (or power line modem). Thefiltering criteria may be supplied from the PLS (which may be based onrequests received from the user) and is stored in memory of the PLB 400and may form part of the routing table. The Data Filtering software mayanalyze the data packets and may prevent the transmission of datapackets through the PLB:1) that are transmitted to the user device froma particular source (e.g., from a particular person, user, domain name,email address, or IP or MAC source address); 2) that are transmittedfrom the user device to a particular destination (e.g., to a particularperson, email address, user, domain name, or IP or MAC destinationaddress); 3) that have particular content (e.g., voice data or videodata); 4) based on the time of transmission or reception (e.g., times ofthe day and/or days of the week); 5) that surpass a threshold quantityof data (either transmitted, received, or combination thereof) for apredetermined window of time (e.g., a day, week, month, year, orsubscription period); or 7) some combination thereof.

Auto-Provision and Activation of Network Components

“Auto-Provisioning” is the term used that may be used to refer to thesteps performed to get a new network element (e.g., a PLB, repeater, orbackhaul point 10) onto the PLCS network. While skilled in working withpower lines, personnel installing the PLBs 400 (linemen) often havelittle or no experience in working with communication networks.Consequently, it is desirable to have a system that permits easyinstallation of the PLBs 400 without the need to perform networkconfiguration or other network installation procedures.

In the present example embodiment, each network element includes aunique identifier, which may be a serial number. In this embodiment, theenclosure of the PLB 400 has a barcode that the installer scans torecord the serial number. The installer also records the location of theinstalled device. This information (the identifying information andlocation) is provided to a network administrator to input theinformation into the PLS. Alternately, the installer may wirelesslytransmit the information to the PLS for reception and storage by thePLS.

In one example embodiment, after being physically installed and poweredup, the PLB 400 transmits a request, such as a dynamic hostconfiguration protocol (DHCP) request, to the BP 10 with whom thecommunication device is physically or functionally connected. Inresponse to the request, the BP 10 assigns and transmits an IP addressto the MV interface 200 (i.e., assigns an IP address to be used tocommunicate with the MV modem 280), and the MV subnet mask. In addition,the BP transmits the IP address of the BP 10 to be used as the PLB'snetwork gateway address, and the IP address for the PLS. The PLB 400receives the information from the BP 10 and stores it in itsnon-volatile memory.

The PLB 400 then transmits an Alive Alert to the PLS (using the IPaddress received in response to the DHCP request) indicating that thePLB 400 is running and connected to the network. The Alive Alert mayinclude information identifying the PLB, network configurations of thePLB 400 (e.g., MAC addresses of the LV modem 450 and MV modem 280), theIP address of the MV Interface (i.e., the IP address assigned to the MVmodem 280 received from the BP 10) and MV subnet mask for use by thecommunication device's backhaul interface (much of which was receivedfrom the BP 10). This information is stored by the PLS in the networkelements database.

In response, the PLS may activate the PLB 400 by assigning andtransmitting the PLB 400 a LV subnet mask and a LV Interface IP address(i.e., the IP address used to communicate with the LV modem 450). Ifthere are customers present on the LV subnet, the PLS will transmitcustomer information to the PLB, which may include such information asdata filtering information, keys (e.g., encryption keys), user device IPaddresses, and subscription levels for the various users and/or userdevices. In addition, the PLS may configure the PLB 400 by transmittingDNS addresses (e.g., a first and second DNS address), and a registrationserver IP address. This information is stored by the PLS (in the networkelements database) and the PLB. As discussed below, until a user deviceis registered, the PLB 400 may be programmed to allow the user device toaccess only the domain name servers and registration server.

Provisioning a New User Device

Similarly, when a user installs a new user device on the LV subnetattached to the PLB, the user device may need to be provisioned toidentify itself on the network. To do so in this embodiment, the newuser device transmits a DHCP request, which is received and routed bythe PLB 400 to a DHCP server running in the controller 470 of the PLB.In response to the request, the PLB 400 may respond by transmitting tothe user device the IP address and subnet mask for the user device, thegateway IP address for the device's network interface to be used as thenetwork gateway (e.g., the IP address of the LV modem 450 of the PLB),and the IP addresses of the Domain Name Servers (DNS) all of which arestored in memory by the user device. In addition, the PLB 400 maytransmit a new user device Alert to the PLS.

After provisioning, it may be necessary to register the user device withthe network, which may require providing user information (e.g., name,address, phone number, etc.), payment information (e.g., credit cardinformation or power utility account information), and/or otherinformation to the registration server. The registration server maycorrelate this information with information of the utility company orInternet service provider. The registration server may form part of, orbe separate from, the PLS. Until registered, the PLB 400 prevents theuser device (through its power line modem 50) from communicating with(receiving data from or transmitting data to) any computer other thanthe registration server or the two DNSs. Thus, until the user device isregistered, the PLB 400 may filter data packets transmitted to and/orfrom the user device that are not from or to the registration server ora DNS. In addition, requests (such as HTTP requests) for other Internetweb pages may be redirected and transmitted as a request for theregistration web page on the registration server, which responds bytransmitting the registration web page. Control of access of the userdevice may be performed by limiting access based on the IP address ofthe user device to the IP addresses of the registration server and DNSs.

After registration is successfully completed, the registration servercommunicates with the PLS to provide registration information of theuser device to the PLS. The PLS transmits an activation message for theuser device (or power line modem) to the PLB. In response, the PLB 400removes communication restrictions and permits the user device (andpower line modem 50) to communicate through the PLCS to all parts of theInternet. As will be evident to those skilled in the art, filtering ofdata and controlling access of the user device may be performed bylimiting access based on the IP address of the user device (or dependingon the network communication protocol, the MAC address of the userdevice) or the MAC address of the power line modem 50 to which the userdevice is connected. Thus, the PLB 400 may compare the source IP address(or MAC address) with information in its memory to determine if the IPaddress (or MAC address) is an address that has been granted access tothe PLCS. If the source address is not an address that has been grantedaccess to the PLCS (e.g., by registering, which results in an activationmessage from the PLS to the PLB), the PLB 400 may replace thedestination IP address of the packet with the IP address of theregistration server and transmit the packet to the backhaul point. Theprocedure above, or portions of the procedure, with respect toprovisioning user devices may be used to provision a power line modeminstead of or in addition to a user device.

Alternate Embodiments

As discussed, the PLB 400 of the above embodiment communicates datasignals to user devices via the LV power line. Rather than communicatingdata signals to the power line modem and/or user devices via the LVpower line, the PLB 400 may use other communication mediums. Forexample, the PLB 400 may convert the data signals to a format forcommunication via a telephone line, fiber optic, cable, or coaxial cableline. Such communication may be implemented in a similar fashion to thecommunication with LV power line as would be well known to those skilledin the art.

In addition, the PLB 400 may convert the data signal to radio signalsfor communication over a wireless communication link to the user device.In this case, user device may be coupled to a radio transceiver forcommunicating through the wireless communication link. The wirelesscommunication link may be a wireless local area network implementing anetwork protocol in accordance with an IEEE 802.11 (e.g., a, b, or g)standard.

Alternatively, the PLB 400 may communicate with the user device via afiber optic link. In this alternative embodiment, the PLB 400 mayconvert the data signals to light signals for communication over thefiber optic link. In this embodiment, the customer premises may have afiber optic cable for carrying data signals, rather than using theinternal wiring of customer premise.

In addition to or instead of a wired connection or fiber connection, theMVID 300 may include a transceiver such as a wireless transceiver forcommunicating with the AP 100 or DP 200 wirelessly (e.g., an 802.11wireless link) and/or the PLBs. Likewise, the CMTS may alternatelycommunicate with the DP 200 via a wireless connection.

Thus, the AP 100 may communicate with the DP 200 or MVID 300 via aWireless Modem Termination System (WMTS) and a hub transceiver antennaat the base station, and a transceiver antenna at the DP 200 or MVID.Preferably, the system uses DOCSIS-compatible protocols and offersscalability and measurable Quality of Service (QoS). Such a systemcommercially available from Arcwave located at 910 Campisi Way #1C,Campbell, Calif. 95008 in there ARCXtend™ Wireless Plant ExtensionSolution, which includes their ARCell products. The wireless link may bein the license-free 5 GHz bands or in a different and licensed band.

In another embodiment, the wireless link is provided via the ARCXtendWireless Plant Extension solution by Arcwave. In another embodiment, theDL-5800 by Wireless Bypass, Inc., which also wirelessly communicateswith DOCSIS protocols may be use for bi-directional communications.

In addition, the controller 470 of this embodiment may includesubstantially the same software and functionality as that described withrespect to the PLB 400 and modifications thereto would be readilyapparent to one skilled in the art.

Miscellaneous

As discussed, the functions of the power line modem may be integratedinto a smart utility meter such as a gas meter, electric meter, or watermeter. The meter may be assigned an IP address by the PLCS (e.g., by thePLS) and, upon receiving a request or at predetermined intervals,transmit data such as consumption data to the PLB, the PLS, and/or autility computer system in a manner described herein, therebyeliminating the need to have utility personnel physically travel to readthe meter. In addition, one or more addressable switches, which may formpart of a utility meter, may be controlled via the PLCS (e.g., withcommands transmitted from the PLB, the PLS, and/or utility computersystem) to permit connection and disconnection of gas, electricity,and/or water to the customer premises.

Similarly, the PLCS may be used to control MV power line switches. Theaddressable MV power line switch may be a motorized switch and assignedan IP address by the PLS, which is also provided to the utility computersystem to thereby operate the switch. When a power outage is detected,the utility company may remotely operate one or more addressable MVpower line switches to provide power to the area where the outage isdetected by transmitting commands to the IP addresses of the switches.

Likewise, the PLCS may be used to operate a capacitor switch thatinserts or removes a capacitor (or capacitor bank) into the powerdistribution system. Capacitor banks are used to improve the efficiencyof the power distribution network by providing Volt/VAr management(e.g., modifying the reactance of the power distribution network). Thus,the PLS may assign an IP address to one or more capacitor switches,which is also provided to the utility computer system to thereby operatethe switch. Based on power quality measurements taken and received fromone or more PLBs, the utility company may insert or remove one or morecapacitor banks by remotely actuating one or more capacitor bankswitches by transmitting commands to the IP addresses of the switches.

The capacitor switch and the MV power line switch may be controlled byan embodiment of the present invention that includes a MV interface andcontroller. In addition, in some embodiments a LV interface may also beemployed.

The power line modem in the above embodiments has been described as adevice that is separate from the user device. However, the power linemodem may also be integrated into and form part of the user device.

While the above described embodiments utilize a single modem in the LVinterface and the in the MV interface, alternate embodiments may use twomodems in the LV interface and/or two modems in the MV interface. Forexample, the LV interface may comprise a receive path (for receivingdata from the LV power lines) that includes a LV modem and signalconditioning circuitry and a transmit path (for transmitting datathrough the LV power lines) that includes a second LV modem and signalconditioning circuitry. Each LV modem may have a separate address (MACand IP address) and operate at a separate frequency band. Thus, thereceive or transmit LV interfaces may also include frequency translationcircuitry.

Likewise, as another example the MV interface may comprise a receivepath (for receiving data from the MV power line) that includes a MVmodem and signal conditioning circuitry and a transmit path (fortransmitting data through the MV power line) that includes a second MVmodem and associated signal conditioning circuitry. Each MV modem mayhave a separate address (MAC and IP address) and operate at a separatefrequency band. Thus, the receive or transmit MV interfaces may alsoinclude frequency translation circuitry. A repeater may also beconstructed with multiple MV modems in both of its MV interfaces or inits only MV interface as the case may be.

While the described embodiments may apply the data signals to one MVconductor (and the data signals may couple to other conductors), otherembodiments may apply the data signals differently. For example, a firstMV coupler (and an associated MV interface) may be coupled to a first MVconductor for transmitting data on the MV conductor and a second MVcoupler may be coupled to a second MV conductor for receiving the returncurrent of the transmitted data. The two couplers may thus share asignal MV modem. Similarly, the first and second couplers (coupled tothe first and second MV power line conductors) may transmit (andreceive) the data signals differentially as described above in thecontext of the LV power line transmissions and shown in FIGS. 6 b and 6c. Thus, the same data signal may be transmitted down multiple MVconductors with the signal on each conductor being phase shifted (e.g.,120 degrees or 180 degrees) with respect to the signal(s) on the otherconductor(s). Alternately, in any of these embodiments, the neutralconductor may be used (e.g., as a return path or separate transmissionpath) instead of one or more of the MV conductors.

The PLBs 400 may communicate with the user devices via low voltagerepeater. An example of such a repeater is described in U.S. patentapplication Ser. No. ______, entitled, filed ______, which is herebyincorporated by reference in its entirety

As will be evident to those skilled in the art, the MVIDs 300 and powerline modem for communicating with these alternate embodiments of thebypass device (or repeater) would also require similar circuitry fortransmitting and receiving with multiple modems and in the differentfrequency bands. More specifically, the modified power line modem wouldalso require a first and second modem for transmitting and receiving,respectively, and designed to operate in the appropriate frequency bandsfor establishing communications. Such a system would permit full duplexcommunications through the power lines.

In the above embodiment, the processor performs routing functions andmay act as a router in some instances and perform other functions atother times depending on the software that is presently being executed.The router may also be a chip, chip set, or circuit board (e.g., such asan off the shelf circuit card) specifically designed for routing, any ofwhich may include memory for storing, for example, routing information(e.g., the routing table) including MAC addresses, IP addresses, andaddress rules.

While the above description describes communications between the MVIDs300 and DPs to be via optical, wireless, T1, or coaxial cablecommunication medium, the communications may also be accomplished byusing over a MV power line or neutral conductor using conductiveelectrical signals or surface waves.

Finally, the type of data signal coupled by the coupling device may beany suitable type of data signal. The type of signal modulation used canbe any suitable signal modulation used in communications (Code DivisionMultiple Access (CDMA), Time Division Multiple Access (TDMA), FrequencyDivision Multiplex (FDM), Orthogonal Frequency Division Multiplex(OFDM), and the like). OFDM may be used on one or both of the LV and MVpower lines. In addition, DOCSIS signals may be used on the MV powerlines and over the fiber optic conductors in the above describedembodiments. A modulation scheme producing a wideband signal such asOFDM or CDMA that is relatively flat in the spectral domain may be usedto reduce radiated interference to other systems while still deliveringhigh data communication rates.

It is to be understood that the foregoing illustrative embodiments havebeen provided merely for the purpose of explanation and are in no way tobe construed as limiting of the invention. Words used herein are wordsof description and illustration, rather than words of limitation. Inaddition, the advantages and objectives described herein may not berealized by each and every embodiment practicing the present invention.Further, although the invention has been described herein with referenceto particular structure, materials and/or embodiments, the invention isnot intended to be limited to the particulars disclosed herein. Rather,the invention extends to all functionally equivalent structures, methodsand uses, such as are within the scope of the appended claims. Thoseskilled in the art, having the benefit of the teachings of thisspecification, may affect numerous modifications thereto and changes maybe made without departing from the scope and spirit of the invention.

1. A system for providing communications to user devices via anunderground power line comprising a plurality of segments disposed inseries with each other and carrying a power signal having a voltagegreater than one thousand volts, comprising: an interface devicecommunicatively coupled to the underground power line and having aninterface configured to be communicative via a non-power linecommunications medium; a first and second power line communicationsdevice, each said power line communications device including a firstport communicatively coupled to the underground power line forcommunications with said interface device and a second port incommunication with the one or more user devices; wherein said firstpower line communications device is communicatively coupled to the powerline at a location closer to the interface device than said second powerline communications device; wherein said interface device is configuredto transmit communications signals to said first and second power linecommunications devices in a first set of frequencies and said first andsecond communications devices are configured to receive communicationsin the first set of frequencies; and wherein said first and second powerline communications devices are configured to transmit communicationssignals toward said interface device in a second set of frequencies andsaid interface device is configured to receive communications in thesecond set of frequencies.
 2. The system of claim 1, wherein said firstpower line communications device comprises: a first amplifier circuitconfigured to amplify first signals received from said second power linecommunications device in the second set of frequencies; and a couplerconfigured to couple the amplified signals onto the power line.
 3. Thesystem of claim 1, wherein said first power line communications deviceis configured to receive data signals received from the one or more userdevices and to transmit at least some of the received signals to saidinterface device.
 4. The system of claim 2, wherein said first powerline communications device includes a second amplifier circuitconfigured to amplify second signals received from said interface devicein the first set of frequencies.
 5. The system of claim 4, wherein saidfirst power line communications device further comprises a secondcoupler configured to couple the second amplified signals to the powerline.
 6. The system of claim 1, wherein said first power linecommunications device further comprises: a first amplifier circuitconfigured to amplify signals received from said interface in the firstset of frequencies; and a coupler configured to couple the amplifiedsignals onto the power line.
 7. The system of claim 2, wherein saidfirst power line communications device further includes a CableLabsCertified Cable Modem.
 8. The system of claim 1, wherein said first andsecond said power line communications devices each include a router. 9.The system of claim 1, wherein said first and second power linecommunications device each include a cable modem substantially compliantwith a DOCSIS specification.
 10. The system of claim 1, wherein thefirst and second power line communications device are configured totransmit to said interface device using time division multiplexing. 11.The system of claim 1, wherein the first and second power linecommunications devices are configured to transmit to said interfacedevice using CDMA.
 12. The system of claim 1, wherein said interfacedevice is communicatively coupled to the Internet via a cable modemtermination system.
 13. The system of claim 1, wherein said second portof said first power line communications device is communicativelycoupled to a low voltage power line to provide communicationstherethrough to the one or more user devices.
 14. The system of claim13, wherein said first line power line communications device isconfigured to communicate with the user devices via a third set offrequencies.
 15. The system of claim 1, wherein said first power linecommunications device is disposed in a transformer enclosure.
 16. Thesystem of claim 1, wherein said wherein said first and second power linecommunications device are configured to receive and process a pluralityof DOCSIS commands.
 17. The system of claim 1, wherein the non-powerline communications medium comprises a fiber optic conductor.
 18. Thesystem of claim 1, wherein the non-power line communications mediumcomprises a wireless link.
 19. The system of claim 1, wherein saidinterface device is communicatively coupled to the power line at a riserpole.
 20. A system for providing communications via one or more powerlines carrying a power signal having a voltage greater than one thousandvolts, comprising: an aggregation device; a plurality of distributiondevices communicatively coupled to said aggregation device via anon-power line communications medium; a plurality of interface devices,each said interface device communicatively coupled to one of the powerlines and each said power line interface device communicatively coupledto one of said plurality of said distribution devices via a non-powerline communications medium; a plurality of power line communicationsdevices, each said power line communications devices comprising a firstport and second port, said first port and said second portcommunicatively coupled to one of the power lines for communicationswith one of said plurality of interface devices, said plurality of powerline communications device including a third port communicativelycoupled to a low voltage power line, each said power line communicationsdevice including a first modem in communications with said first port; asecond modem in communications with said first modem and said thirdport; and a router in communication with said second modem.
 21. Thesystem of claim 20, wherein at least one of said plurality ofdistribution points is communicatively coupled to said aggregationdevice via one or more fiber optic conductor.
 22. The system of claim20, wherein said aggregation device includes a cable modem terminationsystem.
 23. The system of claim 20, wherein said interface deviceincludes an interface configured to communicate via one or more fiberoptic conductors and an electrical-to-optic converter communicativelycoupled to said interface.
 24. The system of claim 20, wherein at leastone of said plurality of power line communications devices includes: afirst amplifier having an input and an output and configured to amplifydata signals in a first frequency band, said output of said firstamplifier being communicatively coupled to said first port and saidinput of said first amplifier being communicatively coupled to saidsecond port; and a second amplifier configured to amplify data signalsin a second frequency band; said output of said second amplifier beingcommunicatively coupled to said second port and said input of saidsecond amplifier being communicatively coupled to said first port. 25.The system of claim 20, wherein said first modem of said plurality ofpower line communications devices includes a cable modem
 26. The systemof claim 25, wherein said cable modem is configured to receive andprocess a plurality commands substantially compliant with a DOCSISspecification.
 27. The system of claim 1, wherein the non-power linecommunications medium communicatively coupling at least on of theplurality of interface devices to one of said plurality of distributiondevices comprises a fiber optic conductor.
 28. The system of claim 27,wherein a first of said plurality of interface devices iscommunicatively coupled to one of said plurality of distribution devicesvia a second of said plurality of said interfaces.
 29. The system ofclaim 28, wherein said second of said plurality of interface device isconfigured to combine data from said first of said plurality ofinterface devices with data from said second of said plurality ofinterface devices for communication to said one of said plurality ofdistribution devices via a fiber optic conductor.
 30. The system ofclaim 20, wherein the non-power line communications mediumcommunicatively coupling at least on of the plurality of interfacedevices to one of said plurality of distribution devices a wirelesslink.
 31. A method of providing communications to user devices via anunderground power line comprising a plurality of segments disposed inseries with each other and carrying a power signal having a voltagegreater than one thousand volts, comprising: at an interface device:receiving first data via a non-power line communications medium; andtransmitting said first data in a first frequency band via the powerline; at a first power line communications device; receiving the firstdata in a first data signal from the interface device; amplifying thefirst data signal; coupling the amplified first data signal in the firstfrequency band to the power line; and at a second power linecommunications device; receiving the first data signal; and demodulatingthe data signal to provide the first data.
 32. The method of claim 31,further comprising demodulating the first data signal at the first powerline communications device.
 33. The method of claim 31, furthercomprising: at the second power line communications device: modulatingthe first data to provide a second data signal; and transmitting thesecond data signal to a user device via a low voltage power line. 34.The method of claim 33, further comprising routing the first data priorto modulating the first data at the second power line communicationsdevice.
 35. The method of claim 31, further comprising routing the firstdata at the second power line communications device.
 36. The method ofclaim 31, further comprising: at the second power line communicationsdevice: receiving second data transmitted from a user device; andtransmitting the second data in a second frequency band via the powerline; at a first power line communications device; receiving the seconddata in a second data signal from the second power line communicationsdevice; amplifying the second data signal; and coupling the amplifiedsecond data signal in the second frequency band to the power line; andat the interface device: receiving the second data signal; andtransmitting the second data via a non-power line communications medium.37. The method of claim 36, further comprising: at the second power linecommunications device: receiving the second data via a low voltage powerline signal; and demodulating the low voltage power line signal toprovide the second data.
 38. The method of claim 37, further comprisingrouting the second data at the second power line communications device.39. The method of claim 36, further comprising: at the first power linecommunications device: receiving third data from a user device; andtransmitting the third data in the second frequency band via the powerline; and at the interface device: receiving the third data; andtransmitting the third data via a non-power line communications medium.40. The method of claim 31, wherein the first data is amplified by athird power line communications device coupled to the power line betweenthe first power line communications device and the interface device: 41.The method of claim 31, wherein the non-power line communications mediumincludes a fiber optic conductor.
 42. The method of claim 31, whereinthe non-power line communications medium includes a wireless link. 43.The method of claim 31, wherein the first frequency band includes atleast some frequencies between thirty megahertz and fifty megahertz. 44.The method of claim 31, further comprising frequency shifting thesignals carrying the first data at the interface device.
 45. The methodof claim 31, wherein the first data includes a DOCSIS command or DOCSISstatus request.
 46. The method of claim 31, wherein the interface deviceis communicatively coupled to the Internet via a CMTS.
 47. The method ofclaim 31, wherein the amplifying of the first data signal is performedwithout modulation.
 48. A method of providing communications to userdevices via an underground power line comprising a plurality of segmentsdisposed in series with each other and carrying a power signal having avoltage greater than one thousand volts, comprising: at a first powerline communications device; receiving first data; and transmitting thefirst data via the power line; at a second power line communicationsdevice; receiving the first data in a first data signal from the secondpower line communications device; amplifying the first data signal; andcoupling the amplified first data signal via the power line; and at aninterface device: receiving the first data signal; and transmitting thefirst data via a non-power line communications medium; and whereintransmissions from the second power line communications device and theinterface device employ different carrier frequencies.
 49. The method ofclaim 48, further comprising: at the second power line communicationsdevice: receiving second data from a user device; transmitting thesecond data via the power line.
 50. The method of claim 49, whereintransmissions toward the interface device from the first and secondpower line communications device are via time division multiplexing. 51.The method of claim 49, further comprising routing the second data atthe first power line communications device.
 52. The method of claim 48,wherein the non-power line communications medium includes a fiber opticconductor.
 53. The method of claim 48, wherein the non-power linecommunications medium includes a wireless link.
 54. The method of claim48, further comprising frequency shifting the signal carrying the firstdata at the interface device.
 55. The method of claim 48, wherein thefirst data includes a DOCSIS command or DOCSIS status request.
 56. Themethod of claim 48, wherein the interface device is communicativelycoupled to the Internet via a CMTS.
 57. A system for providingcommunications to user devices via a power distribution networkcomprising an underground power line carrying a power signal having avoltage greater than one thousand volts, and a plurality of low voltagepower lines with each low voltage power line receiving power from theunderground power line via a distribution transformer, the systemcomprising: an interface device communicatively coupled to theunderground power line and having an interface configured to becommunicate via a non-power line communications medium; a first andsecond power line communications device, each said power linecommunications device including a cable modem coupled to the undergroundpower line and a power line modem communicatively coupled to one of thelow voltage power lines; wherein said first power line communicationsdevice is communicatively coupled to the underground power line at alocation closer to the interface device than said second power linecommunications device; and wherein said first power line communicationsdevice includes an amplifier configured to amplify received signalstransmitted by said interface device and a first coupler configured tocouple the amplified signals to the power line for reception by saidsecond power line communications device.
 58. The system of claim 57,wherein said first power line communications device is configured toamplify the received signals for coupling onto the underground powerline by said first coupler without demodulation.
 59. The system of claim57, wherein: said power line modem of said first power linecommunications device is configured to receive data signals receivedfrom user devices; and said cable modem is configured to transmit atleast some of the received signals to said interface device via theunderground power line.
 60. The system of claim 59, wherein said firstpower line communications device includes a second amplifier circuitconfigured to amplify received signals transmitted from said secondpower line communications device; and a second coupler configured tocouple the signals received from said second power line communicationsdevice and amplified to the underground power line for reception by saidinterface device.
 61. The system of claim 60, wherein said secondcoupler communicatively couples said cable modem of said first powerline communications device to the underground power line.
 62. The systemof claim 57, wherein: said interface device is configured to transmitcommunications signals to said first and second power linecommunications devices in a first set of frequencies and said first andsecond power line communications devices are configured to receivecommunications in the first set of frequencies; and said first andsecond communications devices are configured to transmit communicationssignals toward said interface device in a second set of frequencies andsaid interface device is configured to receive communications in thesecond set of frequencies.
 63. The system of claim 62, wherein saidpower line modem of said first and second line power line communicationsdevices are configured to communicate with user devices via a third setof frequencies.
 64. The system of claim 57, wherein said first andsecond said power line communications devices each include a router. 65.The system of claim 57, wherein said cable modem of said first andsecond power line communications device are each substantially compliantwith a DOCSIS specification.
 66. The system of claim 57, wherein thefirst and second power line communications device are configured totransmit to said interface device using time division multiplexing. 67.The system of claim 57, wherein said first and second power linecommunications devices are configured to transmit to said interfacedevice using code division multiplexing.
 68. The system of claim 57,wherein said interface device is communicatively coupled to the Internetvia a cable modem termination system.
 69. The system of claim 57,wherein said first power line communications device is disposed in atransformer enclosure.
 70. The system of claim 57, wherein said whereinsaid first and second power line communications devices are configuredto receive and process a plurality of DOCSIS commands.
 71. The system ofclaim 57, wherein the non-power line communications medium comprises afiber optic conductor.
 72. The system of claim 57, wherein the non-powerline communications medium comprises a wireless link.
 73. The system ofclaim 57, wherein said interface device is communicatively coupled tothe underground power line at a riser pole.
 74. The system of claim 61,wherein coupling of signals to the underground power line by said secondcoupler from said cable modem of said second amplifier is via timedivision multiplexing.